Of course you can. Because Biden won't be on the tv or his cellphone everyday blatantly lying with absolute bullshit that gets refuted immediately.
Obama killed more people [including two separate wedding parties, I believe both in Pakistan] than any president in history before him [and I think since - as I don't recall hearing Trump doing that, and if he did, I would be surprised if he did more than Obama].
Is that not a valid issue to complain about? Or the increase in taxes on the middle class? Or mass-importing millions of people each year from the developing world in order to get more Democrat voters [and cheap labour for Republicans]?
Or how about the massive amount of riots caused exclusively in Democrat-ran cities, who seem to have a problem with not only Trump, but with their own Democrat city and state leadership, for not being "Woke" enough?
So no - it's not true that we who support Trump don't have a valid reason for being upset with Biden's presidency.
For me, especially being in Canada, I don't think it's the end of the world if Biden wins.
I am curious to see how far he declines cognitively throughout his term though. Keep me mind that he has a slightly over 50% chance of dying within the next four years. Those numbers are probably even higher if he is, in fact, in the early stages of dementia.
I'm curious to see how that plays out.