Having a grievance with a game because of a certain characters exclusion isn't necessarily unfounded. I mean, sure, if you expect a character and convince yourself a character is in the game and then hold a grudge against the game because said character isn't there may be a bit overboard but being disappointed that a character isn't there isn't a crime.
For instance, I loved Smash For. I adored it, but every time I turned that game on a felt like something was missing. I played Brawl through and through with 3 character. Snake, Wolf, and Ike. And two of those characters didn't make it back. That was super disappointing to me and I felt like because of those cuts Smash For was the worst Smash game in the franchise. Now is that necessarily true? No, but I can say with 100% confidence that it was the one that disappointed me the most. Losing Snake was tough. Real tough. Still, looking back on Smash For, the roster for the game, especially when including DLC, was really solid for the time. Pac-Man, Mega Man, Ryu, Cloud, Little Mac, Rosalina, Shulk, Robin, Greninja, etc. All great choices but there was still that one, or two, missing thing(s) and that just disappointed me every time I played.
The point is you don't have to be sour on the game because of the lack of a character, but being disappointed isn't exactly a damning thing. We have wants, they don't happen sometimes, that's ok. Just count the blessings you have now and hope for the best in the future. I mean it worked for me and my characters, Ridley, K. Rool, and Simon included. It could work for yours.