1. Everything's gotten way too grindy. It wasn't too bad, back when you just had to grind for energy, crowns, heat, and a few crafting materials. Now you have to grind for orbs and shards as well - just to do the same things we used to do without grinding for them. Yeah, it sucked having to use energy just to use the lift, but we got the mist energy for free, so it wasn't too bad.
2. The only actual new level types I can remember since I started playing suck. They suck so bad that frequently, players will wait for a different level type rather than play them, which can mean 5-10 minutes of doing nothing. These levels are Candlestick Keep and the stupid Burrows. Yes, people would literally rather sit around doing NOTHING than play these. These levels sucked when they were first released, however long ago that was (probably a couple years by now). They still suck. Why are they still here? The game would literally be more fun if they were simply removed. Where's some new content that's actually good?
3. Way too much crap is monetized. Seriously, this is a game that is *made* to be monetized with cosmetics and fluff. I mean, there's so much potential there compared to other games like LoL or TF2, why does every little thing have to be nickle-and-dime or spend endless hours grinding? Where are the permanent weapon and trinket slot upgrades?
I never actually "quit" this game, so much as just lost interest and stopped playing. Tried playing it again the last couple days, and nothing's changed since the last time I tried a few months ago. It's still the same grindy pile of crap it became over the last few years. Maybe it's time to finally cut the cord completely.
I actually really enjoy compounds (what you called burrows) and candlestick keep. I do not enjoy the payout of compounds or see the payout of candlestick keep as being high enough to seek out, but I do enjoy playing on the levels. Compounds in particular was always a really nice change of pace for me whenever I encountered it- the game went from focusing on small 3-5 enemy encounters to being much more centered on area of effect. If only the loot wasn't so awful..
The game would be considerably less grindy if it weren't for those radiant fire crystals but because they are here you are very much correct in that everything's gotten too grindy. I'd point to the events as examples of less grind and more fun, but 10,000 sigils and 6 whiskers have something to say about that.. so yes, the game does feel very monetized.