Why do modern JRPGs feel less like actual adventures than the

Reliance on voice acting and set dressing.
If every scene needs to be orchestrated and produced it is limiting on what you can do

One is an adventure game while the other is a cinematic experience.

Variety, less complexity. Some focus on exploration. No using modern RPG mechanics.

Today most JRPGs have a different focus unless they're made to appeal to classic JRPG players (such as newer Dragon Quest games). Now everyone wants to reinvent the wheel.

Also consider this is Final Fantasy. It changes drastically in every entry, specially the latest ones. Gameplay is absurdly different between one entry and another. They put too much focus in battle mechanics and cinematics (these features arguably sold a few PS1 RPGs, but still) and not a whole lot into anything else.