idk dude i don't think there's a media conspiracy to make Biden look old and senile, at least speaking of ABC, CBS, CNN etc. they tend to go out of their way to talk about how good the economy is or lavish him with praise whenever he goes on international trips, or conspicuously not run the glaring gaffs that are viral at the moment.
I remember when he crushed the Railroad strike and the way NBC covered the News was immediately pivoting to how the economy is doing great look at these numbers!
You can contrast the media portrayal of Biden speaking at Hawaii or Vietnam with the clips that were easy to find on any social media site, where he rambles incoherently and just says weird or not true things, of course critics of Biden on left and right would zero in on this but, it also goes viral because it's just fucking funny as shit
Also compare how Biden's televised statements are carefully selected, with how Trump would get unedited rant time on every media...
Personally, instead of saying there's a media conspiracy to smear Biden in particular, the media is *hostile* to literally every Presidential Administration because controversy sells, but probably has a marginal preference to Biden over Trump for reasons that should be obvious.