I don't think the issues have changed much from the players' perspective. They think that NBA-style revenue sharing is going to reduce their take. I'm not sure their thinking make sense to me but as they say, it is what it is. At any rate, does this article help:
https://www.royalsreview.com/2022/2/18/22940181/what-would-an-nba-style-salary-floor-and-salary-cap-look-like-for-mlb?
In addition, although I've not seen anyone come out and say it, I think another issue for the players is that at least for the NBA, if basketball-related revenues go down significantly, players have to take a haircut. From my recollection of the negotiations for the return of baseball in 2020, it seemed that the players thought since the owners get the majority of the upside of ownership, they should also take the majority of the downside when revenues tank. The NBA CBA has provisions that if the players' share of basketball-related revenues goes over a certain percentage, then a portion of salaries are withheld until the appropriate split is met. Thus, the NBA CBA requires the players to pick up a good bit of the downside and I doubt the MLBPA would agree to that (for better or for worse).
As mentioned upthread, I'm not an expert on the NBA or NFL salary caps but it's my understanding that neither attempts to take into account all revenue. It just defines certain revenue as the pot being shared - primarily gate, broadcast, sponsorships, and merchandise - and then splits up that pie. There are revenues that it's my understanding (I'm sure people will correct if I'm wrong) that aren't split - like real estate development rights around stadiums.
Most of what would be considered "baseball-related income" would be vetted through contractual agreements or the ilk. I'm not aware (again, perhaps I'm wrong about this) about any major accusation from the NFLPA or NBAPA that owners have been systematically understating or hiding revenue that is subject to revenue sharing. And if there is a major source of revenue that is not included, well that can be included by negotiation - like the NBAPA did when they
negotiated to include gambling revenue in "baseketball-related revenue."
I'm not saying that getting to an agreement as to what is "baseball related revenue" and what the percentage split might be is an easy negotiation. It wouldn't be. Particularly when the owners spend a lot of money on talent development, much more than in most other sports, and would probably want it counted against the amount being split up and the parties would not only have to negotiate how the term "baseball-related revenues" is defined and what the appropriate split should be. Still, labor peace would be worth quite a bit - raising the amount of the pie to be split - so I don't understand why the players are so dead set against it.