Ensemble Dark Horse: Among the summon spirits in the various entries, Celsius is easily the most popular of them to the point she was included as a playable character in Radiant Mythology 2 & 3 which based her design from Tales of Eternia.
Friendly Fandoms: Some players of this franchise are also fighting-game players as the combat system is very similar to that of a combo-focused fighting game. It helps that the BlazBlue series was getting started when more Tales of games were coming out internationally alongside of a revitalization of the 2D fighter.
It's the Same, Now It Sucks!: One of the biggest complaints to the point of earning the nickname "Tales of Stagnation". The dated graphics and mechanics are often mentioned, especially when compared to other JRPGs like Final Fantasy.
Seasonal Rot: For some fans this started kicking in with Tales of Graces as most of the games since then have tried their hand at new mechanics and additions to the combat system that some fans feel the Team Symphonia games perfected. If that's not your problem than the fact that the gameplay has become formulaic most likely is. The newer games have also been criticized for having weaker stories and characters, and the signature tropes getting old and predictable. Tales of Zestiria is often seen as the worst example of this trope in the franchise for both gameplay and narrative, though fans have found Tales of Berseria to be a much needed revitalization of the franchise.
"Seinfeld" Is Unfunny: For some of the most veteran fans, the Deconstructor Fleet has been done so many times in the series (both well and badly executed) that it has become a cliché in it on itself by this point. Never mind the fact that someofthegames were considered damn smart in this regard when they came out (some of them still hold up when judged by their own merits, some of them...not so much).