It misses the whole point of the RPG in MMORPG

Roleplaying?

I never said you should not gain gear drops from new bosses. I said the power level of the gear should not exceed that of Tier 2 or Grand Marshall/High Warlord item level.

I'm more in favour of horizontal progression.

Add more talent trees to existing classes

Add more tier sets with diverse stat distribution (but not high item level).

Add spell books that teach new spells and abilities (like shaman earth shield, or paladin and druid taunts)

I wasn't really a fan of the Mythic+ in legion, because I was just doing the same shit but getting +iLvL on the same shit I had.

Neither am I. I hate the +iLvL crap. The affixes in Mythic+ are good way to add a challenge to dungeons though.