You're certainly entitled to your subjective opinion. Just recognize it is subjective.
There are objective aspects: Objectively speaking, one can't argue that Beach Club and Boardwalk are walkable to Epcot, Riviera isn't.
Objectively speaking, one can't argue against the fact that Riviera rooms are bigger than Beach Club and Boardwalk rooms.
Objectively speaking, one can't argue against the fact that Riviera rooms have larger bathrooms with 2 showers.
Objectively speaking, can't argue against the fact that Riviera has fewer rooms than either Beach Club or Boardwalk.
You seem to focus on one thing, your subjective opinion on theming. That's fine, you're not alone. Some people will prefer the theming of Boardwalk or Beach Club, some will prefer the theming of Riviera.
Personally -- I love the theming of the Boardwalk itself, but I can't stand the theming of the actual Boardwalk hotel building. The lobby feels like a stuffy grandparent's house.
While I really like the Beach Club lobby, I find the rest of the resort theming to be bland and non-existent. Okay, it's a pastel blue beachy resort with Holiday Inn quality rooms.
I find Riviera theming to be sophisticated and generally consistent with the European models it is trying to emulate. (though the rooms are much nicer than you'd find in a European hotel).
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Again, opinion will vary. Everyone is entitled to their opinion. To me, Riviera is so much better looking than Boardwalk.