There is more than size going on. Plants are feminine, poison is the weapon of women, Venus is feminine. Her size reads very pre-historic earth mother goddess if you ask me.
Who thinks Venusaur isn't cute. What's not to love about a weird lump with a whole ass flower garden on its back? Actual clown world if anyone thinks Venusaur isn't cute. Or Bulbasaur. Or Ivysaur
Blastoise was my favorite as a boy, but Venusaur is my favorite as a a man. Competitive Gen 3 OU on pokemon showdown has certainly clarified who is powerful and who is not (Venusaur > Charizard > Blastoise in competitive play)
Megas are epic and added a lot to battles and I wish my beloved mega Slowbro wasn't stuck in ORAS. Dynamaxing and terrastalization are busted af though. Z moves are ok