FWIW I think this despite not even thinking he's the most damaging recent President, by a long shot. Yes, even with the whole COVID thing. I'm pretty sure The Other Guy's (I hesitate to distract by naming him) easily safe from ever being lumped in with the notoriously-poor-at-Presidenting set of ex-Presidents—Trump, I think he's got that label in his future.
Whatever they say, the opposite is usually true. When they say "bad at the job" that should be read as "good at the job". Likewise, when they say "good at the job" it means "bad at the job".
People with sense and a love for America do not often become history professors.
[edit] to illustrate: it’s 2080 and you’re a politically-motivated hack historian making a worst ten Presidents list. Do you list 10 political enemies? No. You make 5-8 uncontroversial safe picks, and 2-5 are your political enemies. My contention is that, due to his effectiveness in and execution of the office, Trump is likely to eventually land on a lot of those lists due to being in the “safe pick”, legitimacy-lending category, not the political one. Meanwhile, yes, he’ll be on those plenty for political reasons for the next decade or three.
Despite that, you're quite correct about how historians will rank presidents. Mainly that tells us about historians, but inverting the ratings is almost correct.