I think a big initial appeal of collectathons was that moving in a 3D space was fun, new and you could put a lot of twists on it granddaddy SM64 is still somehow an exemplary.
By the 6th gen the trend was already fizzling out and the games didn't innovate in the right directions. Jak for example mainly did an aesthetic adaptation out of the low-definition fuzzy mascot characters into 2000s grittier ones but didn't provide lasting fun or new twists on gameplay.

Nostalgia and which gen happened in your formative years matters ofc.