I agree with you... 3.6 is a small and meaningless thing
3.6 will have balance changes as well, including Olimar's new up-b as seen in the trailer. Silentdoom (PMDT animator) went on the Olimar Skype group and divulged a bunch of 3.6 Olimar details. The buffs and changes were enough to convince some Olimar mains that he'd be "Top 15 in 3.6."
Delfino's Secret (Dracula's Castle replacement) is also a Page 1 stage that's been resized to be a medium-large starter for competitive use. It'll definitely be seen in tournament and bring a new element to stage counterpicking.
It's not just an aesthetic update, and it's certainly not small or meaningless. The new casual stages, new music, new sound effects, and new costumes are extra. It's fine if you don't appreciate them, but there's more coming in 3.6.
Also, from this point forward, I don't expect there to be any huge changes like 3.5. The cast's playstyles are pretty much defined at this point, and we'll likely only be seeing small engine improvements and necessary balance changes from this point on.