The single most important issue the game needs to tackle to reach the next level is severely reducing the repetitiveness/monotony of various parts of the game
Some context about myself: I only play CoF and I like to experiment and make my own builds, which usually last until like 400-500 corruption where my interest rapidly fades as there are often no more major build changes to look forward to anymore. I've fought normal Aberroth plenty of times, but haven't beaten Uber yet as I don't play meta stuff and get bored before that. Replayability for me comes through levelling new chars or respeccing to try new builds.
Do with that what you want.
This repetitiveness I'm talking about shows in various forms and ways:
\- map layouts are always exactly the same, so even with randomized spawns it becomes repetitive quickly when you know exactly where to go
\- area layouts are often way too large and mob density too low, so you spend more time running than fighting in some areas, which is obviously lame
\- echo webs these days feel pretty boring by default, as their rewards are completely overshadowed by season mechanics and prophecies. Most reward types are boring filler stuff anyway like shards, glyphs, runes, gold, rare items and even exalted nodes are a fart in the wind compared to exalteds you get from mechanics or prophecies, so you just mindlessly click through the web.
This can be improved a bit by placing woven echoes when you have enough amber or stashed echoes or by streamlining echoes into chains through the weaver tree, but it's odd how all of that isn't worked into the echo web generation from the get-go.
It also doesn't help that most amber can be found in tombs and cemeteries, which themselves are often massive in size, yet repeat the same few corridors and enemies over and over.
\- monster variety per echo seems weird aswell as it looks like every echo 2 or 3 monster types are chosen and those get spam spawned everywhere
\- uniqueness between different monsters of the same type is non-existent. Every single siege golem feels the same to fight. Monster modifiers don't feel impactful or relevant at all. I'm not saying I want 1000 homing projectiles or degen ground everywhere like during PoE's worst times, but there's a lot of room inbetween these 2 extremes imo that should be explored.
- dungeons are completely outdated, with massive sizes, but the same 1 or 2 corridor or room types copy pasted to infinity and the lack of season mechanics or any scaled loot there's just no reason to run any of the dungeons without portal charms straight to bosses.
Each of these points don't seem that bad if looked at seperately, but they all add up to this overarching feeling of repetitiveness and monotony that you can feel rather quickly into a season.