If that was the conversation then yes. But when the conversation is about party A fucking up then bringing party B into it is whataboutism. It's the literal definition of a whataboutism.
The meme is about Jimmy Carter running as a candidate for election.... The conversation is clearly about an election in which we are comparing candidates for an election.
This isn't "Joe Biden makes a goddamn awful margarita.", in which "Well putin makes a worse one" would be a whataboutism, this is "Joe Biden is too old to run as a candidate in the election". And in an election, you compare candidates, which is not a logical fallacy.
And we're talking about Jimmy Carter because we're talking about replacing Biden. Telling people to shut up, Trump is worse, is a counter accusation without basis in that context.
Ah, so the idea is that candidates for the position are not yet locked in, therefore comparison between party candidates is not valid. I can get behind that.
However in the current environment I don't see many other paths forward. I think the best alternative I've seen was an article floating al franken. My guess is the original commenters worry is that without viable alternatives, it will likely become a Biden vs trump election, and by then we've provided ourselves with enough negativity against Biden to encourage a trump victory. I'd like to see more positive qualities of alternatives be brought up, instead of negatives about the current most likely nominee.
Well that's the worry. People who want to replace Biden think that his political career is already fatally wounded and it can't get any worse in regards to his election chances.