The worse part of retail is that everything is better… from software user standpoint. But gamers and software users are different things.
Retail is so streamlined to the point of making the whole experience a shallow: 1 run to the shiny/glowing thing, 2 right click to open/kill, 3 loot, rapeat from 1. Everything else is automated or readily available at 2 clicks max.
Classic is the exact same loop but with a lot of distractions trown in from time to time (Blizz and retail players call those “inconveniences”). It is more fun because they break the monotonous grind. Be it you have no bags space - no vendor mount at 1 click, but instead you have monotony breaker of running to city/town (same with trainers). Be it quest objective - no retail objective glow that hits your forehead miles away. Instead (even with Questie) you are required to explore this “inconvenience” called “word” to find the obscure book in that house that questie sent you in. And many, many more similar “inconveniences” that make the experience colorful.
TLDR: You solve the isues that the classic game trows at you (that is called playing) instead of the retail software auto solving your isues.