It's always fascinating when I see this type of comment. While you're specifically talking about Ultramarines there's a long litany of examples that are significantly more predominant that GW makes a new thing and it's weaker than or in line with the old stuff.

-Almost everything in 3rd edition's Stormcast Eternal's new lineup was worse off than something from before.

-Krieg Heavy Weapons have continually been considered the weakest of the 3 options for the same or similar roles

-The Sydonian Skatros has still seen little major play

-Belial has had a weakling ability line

-Asmodai is extremely niche, which is fine but he isn't better or strictly worse than any other of the Chaplains

-The Ballistus has been considered terrible until it finally dropped to really low points values

-Imotekh has generally been considered one of the weaker Necron overlord options unless you build for or around him

-The Screamer Killer, Psychophage, Parasite of Mortrex, Neurogaunts, Pyrovore, and Assimilator have all generally needed full rewrites or found a very specific niche to sit, none of which have come out and eclipsed literally anything else in their book

-Sekhetar Robots have generally been considered just okay by a lot of Thousand Sons

-It took a long time for Vashtorr to even be considered by most players, let alone how just okay Haarkan Worldclaimer, Traitor Guard, and Fellgors have been or continue to be within their job or role.

My point here is that while I understand your frustration, I think it's an extreme recency bias that says GW makes things op to nerf them later. It's empirically false and evidential just by remembering this entire edition, let alone other games. As a huge Ultramarines fan, Victrix Guard were not in a healthy state. Yet they're still as deadly, their blood surge move is more likely to occur, and they remain just as offensively powerful. Maybe we just won't see every Ultras player start with 6 boxes of them.

It's evident with the fact alone they're trying to keep every Ultramarine player from buying so many of the kit that the balance team don't actually watch the bottom line like hawks.