Could you elaborate why each of your examples did not pull it off?
Since apparently not many people are familiar with fighting games:
While Capcom VS SNK 2 was remotely successful, its counterpart SVC Chaos was badly drawn as far as sprites go, loads of hit detection bugs, and the game was even less balanced, having been produced by SNK during its low period where sprites were low quality due to budget restraints.
Tekken 7 has been mostly positive, but Street Fighter X Tekken was a failure mostly because of its DLC and unbalanced mechanics.
Marvel VS Capcom 2, while the most recognized of the games in the series, was originally built for an Arcade setting, so when games like MvC3 came out for game consoles, they were prepping for things like DLC and other gimmicks that weren't all that well thought out (Dictator Magneto for example), not to mention balance issues that were hard to resolve because of the 3 on 3 Team match setup and Assist mechanics that didn't have many variables. (Tier lists in Capcom games are way more apparent than most other games in the genre).
So while they tried to fix that in Ultimate Marvel VS Capcom 3, it... uh.... still didn't balance out very well.
Marvel VS Capcom Infinite had lukewarm reception (as did Street Fighter V with it's missing arcade mode).
Now we have an upcoming game like BlazBlue Crosstag Battle... which, as far as we can see is very polished, BUT.... you can't say that a company like French Bread (Under Night In-Birth / Melty Blood) could produce a BlazBlue crossover game of the same caliber without getting help and money.
POINT BEING: Crossovers look awesome on paper, but not all companies can do them or afford to.
So yeah... even if you LIKE a crossover, chances are, if another company tried to reverse-engineer it, it wouldn't be the same. (for example: if Disney tried to make a Final Fantasy RPG instead of Square-Enix... who KNOWS what would happen... so it's often better for Squeenix to just make Kingdom Hearts instead of someone else).
Tekken 7's DLC with Akuma and Geese evoke memories of Capcom VS SNK 2, but at the same time, it's STILL Tekken in nature, so that was deeply considered. Same expectation for Noctis in Tekken as well.
By contrast, in-series (same company) crossovers are by and large more successful... like Dissidia, Smash Bros, Tales of Versus, Gundam Versus, Dragonball FighterZ, because the formula stays relatively the same.