There's different levels as with everything in life. You can make in person voting more secure too. Nothing is perfect.
Mail-in voting will never be as secure as in-person voting.
So, how bad is "not too bad" when it comes to protecting the democratic process in the US? Nobody is asking for perfect (this is the government, after all). We are asking for common sense measures that prevent cheating -- period. That should not be a partisan issue. Ever wonder why the Democrats are the only party having an issue with voter ID, cleaning up registration roles, ensuring proper observation in all phases of ballot handling and counting, and answering the "Why?" when an anomaly is identified? Cockroaches are afraid of the light.
We do more to protect against cheating on the SAT than we do to ensure election integrity. All SAT tests are still being administered IN PERSON & photo ID is required -- not online, and not via mail-in answer sheets. I guess the pandemic hasn't upended everything, huh?
BTW, you do know states like PA planned to do an all-absentee-ballot election (no justification needed) in October, 2019, long before the pandemic started, right? COVID was just a convenient excuse.