I have also lived on the mainland where there are rail systems and they worked well. I'm sure those systems had their share of criticism. Will rail be as successful on Oahu? who knows.... So......let us not do anything to relieve traffic and sit on it for another 20 years until we are all complaining about our 4hr commutes.
IMHO, something must be done now. Actually, something like rail should have been started 10yrs ago. Traffic is only going to get worse guys, there is no getting around it. Something has got to give. If not rail, then what else has a better shot at relieving traffic? What could be an alternate plan that is long term? expandable? You see the condition of the roads now, can we support new ones?
Anything major will have its growing pains, and Hawaii culture doesn't exactly embrace change.
Japan is crowded, Bankok is crowded, so rail has to work there.......
? Do we wait until Honolulu/Oahu is that crowded, then start a multi-year project? Talk about traffic jams.
Corruption is gonna happen with or without rail. Projects are going to go over budget. It happens. The feds are willing to give us money, we need to run with it.
Either way. If rail happens or not, it won't be the end of the world. If it does, someone will ride it. If someone rides it, that someone is off the road. The more someone's the better and that's better than what will happen if rail doesn't...........nothing.
BTW, I never use H3 but someone does.
Now if we only had lottery income to support things like public education......... 
First off let me cover my background. GZ has a BSc in Civil Engineering. I have design credits in transportation and traffic engineering. I interned with a large construction company on the H3 project and have over 17 years of experience in construction. With this I feel I have a much greater understanding of traffic/transportation than the general layman. Now my take on your observations/comments;
Oahu already has a mass transit system in place. This mass transit system is highly effective. It is called The Bus. This system could become more effective should it be moved to a full/hybrid rapid transit system. By this I mean it would have dedicated travel ways. The good thing about using the current system is it is much more flexible than Rail, it can be adjusted immediately. the skilled labor to maintain the system is already in place, the management system is already in place, the maintenance facilities are already in place, replacement of components is much quicker and can be achieved through purchasing US goods. If you look at the Rail system, it has none of these advantages, rather the money goes outside the US and will require specialized training, maintenance facilities, long lead replacement parts/components/units. The Rail needs to stay on its dedicated path and cannot deviate. Breakdowns of a single component can lead to major delays or flat out shut down of the system. To alleviate this potential you would need to add points at/between stations where you can remove cars from the tracks.
You have mentioned starting something like Rail 10 years ago. Sen Inouye had federal funding lined up for a project such as this in the 90's. Unlike the current system the Federal government would have paid the majority of the bill at that time. Currently without a solid plan to obtain funding, even today's Federal funding may not be guaranteed. This funding issue was raised years ago, but like everything associated with the Rail the City has turned a blind eye. Gross negligence at best.
You ask what can be done to help relieve traffic. For one an alternative plan has already been put forth that will modify the current Bus system to allow for exclusive pathways, it would construct off grade intersections most notably at Piikoi/Vineyard on ramp. Such a split intersection will help greatly to alleviate back log/gridlock at the intersection allowing for greater traffic flow. An elevated reversable toll roadway would still be possible with a terminating point at Aloha Stadium. This point can help to alleviate the daily traffic that gets impacted due to the Pearl Harbor Shipyard workers. Entry onto the toll roadway gives one more way to get the quantities of people out of the area. It will also pay dividends when you look at major sporting or entertainment events held there. For daily traffic it can serve as a way point for the commuters. There is already sufficient parking, will allow for a centralized way point, will allow for a centralized policing of the parked vehicles. The C&C has already stated that they want private partnerships for these station facilities, it's unlikely that you'll be able to do that at all the stations, however you already have that at stadium mall. In addition the tour bus companies can be utilized or the Bus to help shuttle the patrons to their final destinations in downtown Honolulu or to UH. If you consider the cost to do this current line, you must also figure what it would cost to continue a spur to UH. Using the Bus or local tour buses with BRT (Bus Rapid Transit) lanes you can achieve that today at minimal cost, not billions more at the expense of displacing residents along the new spur.
The elevated roadway would be very similar in design and construction to the elevated railway. The maintenance of the roadway will be easier than the railway and factoring in a toll will be more likely to help subsidize itself than Rail where the fee goes towards the car maintenance/repair, rail repair, facility repair, etc.
With regards to going over budget. Yes there are always unforseen conditions however that is not the case with Rail so far. When this was still being discussed the $5B price tag was already mentioned, however Mufi adamantly said it would only be $3B. The initial routing through Salt Lake was done to get Council votes to allow the project to move forward. Once that happened the route was changed to go to the airport where everyone knew it had to go in the first place. That realignment cost money. The realignment by the Federal Building downtown was something that was known, but not addressed. Realignment cost money. The encroachment into the runway approach was known by the City a full year before it was brought to the public's attention, that realignment cost money. Off the top of my head I want to say at least $125+M. The current exploratory shafts for the elevated roadway is ongoing and behind schedule. You want to bet Kiewit has a ton of lawyers reviewing documents and preparing their change orders? These are all items that can and should have been looked at. This points to gross oversight by the City and if more then corruption.
So you see there are viable alternatives that look to help to address the traffic situation, but the City has locked its sights only on Rail. Another way to help is to start strictly enforcing registration and insurance requirements. Registration expired and you're on the street - impound the car and fine. Insurance has expired - impound the car and fine. Things such as window mounted stickers with bar coding can be used to greatly increase the efficiency of the process both in terms of seeing that insurance is in effect, but to also check. Window mounted insurance stickers are already used in other states.
BTW H3 - it was not intended to be a citizen mover. H3 was always intended to be a way to move troops, equipment, and material from KMCBH to Pearl/Hickam in times of national emergency. The benefit derived from it is it has allowed another roadway to travel between the windward and leeward sides.