Right.
To me, the biggest centrist argument against Trump is smack dab in front of our faces right now: His blatant mismanagement of the coronavirus ordeal, the biggest public health crisis of the century. It highlights the importance of competence, at least a rudimentary scientific education, and a willingness to listen to the "experts" that Trump is sorely lacking.
As for me, I turned against Trump for good once I looked into Ukrainegate, and was further disheartened by the subsequent cover-up of this scandal aided and abetted by the GOP Senate.
I was actually willing to accept Trump's flaws up until that point, even through Russiagate (which caught a lot of bad guys but didn't personally implicate Trump himself); however, bribing a foreign country to investigate a political opponent's son was beyond the pale.
That's relatively complex stuff though, and not everyone gets it.