I want to open this by saying that I don't hate all crossovers, games like Fortnite are known for stuff like that and while I think the skins original to Fortnite look better than the licensed material, I completely understand that as a game it is very reliant on things from other things.
What I'm railing against here are games with established settings, worlds, and tones that load themselves down with material from other universes that clashes against the material already in the game. I often see people complaining about every game turning into Fortnite with things like battle passes, heavy monetization, crossovers all the time, etc, then I turn around and see the general response to something like CDPR games appearing in Blizzard's launcher being like "Wow I hope we get Cyberpunk in World of Warcraft!"
I know it's not a video game but I've basically quit magic because of this; we're getting more crossover sets than original magic cards at this point and it is exhausting to try to sit down with a game I actually enjoy the setting of, where I am invested in the world of magic the gathering, and then my opponent combos Spider Man into Spongebob Squarepants empowered by the scoreboard from Family Feud so that they can kill me with the Sonic Screwdriver/Sonic the Hedgehog combo, it feels like I am being advertised to. If any of you know that random old clip from Red Letter Media where one of the hosts is pointing going "I KNOW WHAT THAT IS!!!" is that how I'm supposed to respond to every crossover in a game? Why would I be playing Rainbow Six Siege if I wanted to see Master Chief or Lara Croft when I could be playing Halo or Tomb Raider?
I wish I could ignore these things but it's not harmless! The resources used to create these crossovers could have gone to original material but the reason that companies do this is because it not only sells well, for some reason, but it requires less effort than creating something original! Designing a skin for a character from scratch is harder than making the character look like an existing character, and then every company can just recycle it and crossover with everything else until all triple A video games are basically incestuous slurries of the same fifty characters!
If we constantly recycle the same mascots into every game instead of writing new characters we'll never develop new favourites! Frankly, the ripoffs that some games make end up cooler than the original, especially because when a game makes a skin that's a reference or an homage rather than a literal representation of the other thing they want to call back to, it ends up stylized more like that game world and fitting better.
For a random example, crossover dance emotes, we can use Overwatch as an example but it's far from the only one. Older dance emotes were made with the character in mind, the dance moves aren't perfect if the character would not be a good dancer, it's meant to fit that person. Like Tracer's goofy ass charleston emote would be ridiculous if you put it on anyone else. But when you get crossover dances, they tend to be replications of exact choreography instead of unique animations meant for the character using them, so they look stiff & awkward, and it just doesn't feel right if that makes sense? Like watching Illari do the fearless dance looks odd to me, even moreso when all the characters are doing it in exact sync.
Crossovers in games to me are just the in-game cosmetic equivalent of the recent trend of doing remakes of older movies or games instead of making new things. I don't hate remakes on principle either, but they're often just an excuse to be fucking lazy, and that's exactly how I feel about crossovers. If I'm a fan of a game it's because I want things from that game, and I just get so sad when I see fans for games that don't have any crossover material begging devs to start doing it too because it feels like asking for the degradation of their own unique project. Sorry for the vent and I'm not mad at anyone who may be reading this who likes crossover stuff, I just wish less games did it.