Started playing at 2007 first hero naix mid.
Gonna high light biggest offenders with my opinions in brackets:

Showing jungle spawn boxes
(removal of knowledge requirement)

Showing tower range
(removal of skill and knowledge req, as u can press alt and just dance around the tower range)

Showing skill shot markers
(incredibly useful for blink range)

Showing stun bar/timer
(have to guess or know the stun duration, ppl still fail to chain stun)

(people whined about extra slots, it removes a lot of item complexity. lowering skill ceiling even more. can carry dust wards mangoes healing for free even at late game when things like invisibility we're most powerful because even supports couldnt afford dropping one team saving item to get dust, or should say didnt want to. Removes the need to go to fountain or buy regeneration based items, everyone gets dmg/defensive items only. regen only good on few heroes like storm. Lesh can tp to fountain with scroll and back to action with fairy. Previously you would have a tp scroll in your non dedicated inv slot for that luxury. It's just encouraging brawl dota. Nothing matters except how you take fights and win them, every other little thing is sidelined)

Getting rid of stat upgrades on level up
(this had to go with talents but talents really messed with dota)

Clarity and salve not broken by creeps or towers
(ah anyone remember the pain of salving only to be hit by ranged creep or melee from like 300 range cause they swing so slow... argh)

Wards less money
(wards free now lol)

Wards stacking
(redundant but it still stands, removing complexity of dealing with wards, now anyone can ward or deward at will, in fact i win most of my games just because im warding/dewarding as a carry, in this messed up meta 4-5 picks have to be core capable, so that rules out 95% of support heroes. If its not snapfire/puck/venge/winterwyv ect youre doing it wrong)

Wards fixed hit count and no missing up hill
(even further reducing skill ceiling, where once you could get in time to kill the dewarder who missed possibly 3 times in a row, now you can kill wards in 2 hits always)

Showing ward range before placing
(another skill reduction)

TP slot and starts full
(ratting or playing with enemy tp cooldowns is hard and impossible after they have fairy + scrolls)

TP cheaper
(dont even have to mention what that does)

No cliffing
(with free tps it doesnt matter)

(a noobs crutch. Glad they removed one set of them but they should get rid of them entirely)

Nerfing denies

Fixing several creep manipulation exploits
(like 1st wave pulling.. which was both fun to play with and against. Removing of unique game mechanics is a no from me as it shapes meta in a healthy way. People pick accordingly to deal with multiple waves with more aoe)

Couriers for everyone
(this is possibly the biggest downgrade in every way possible. A call back of icefrog removing bottle crowing to stop "infinite regen" but then gives everyone a courier. This essentially makes laning phase a pointless struggle as anyone can ferry more regen, which encourages dps heavy drafts and less tanky/support picks. (problem for lower mmrs below 5k where people cant quite hold the lead) You almost never have to go to the fountain. Rarely win laning phase. They can just go jungling after 7. It mostly turns out equal or + - 10% either way if draft is balanced. Even if youre more skilled. Thats why veno wins lanes he removes absolute regen advantage. If enemy has only 2/3rds of your regen they cant sustain constant fights.

Couriers being able to use items at lvl 25
(this is odd. They remove anything that requires skill or planning but then adds multi tasking so for people who spam meepos or bears/brood this is a dream adding another 5-10% wr. In late game you cant afford to go and kill couriers with meteor hammers who are queued all around the map to nuke your buildings or waves, even if they die the person loses nothing but some passive gold when they already have more than enough for a buyback)

Jungling after 7 mins.
(Used to be 5 *shudders*. If winning lane is too much bother they can just fall back to jungle come out with 1-2 lucky drops and if not gain an advantage, at least get on equal power level.)

Feel free to add more this cant be all of the problems. Some may not share my exact sentiment, but dota was way better even 2 years back. Theyre stripping the game of interesting ways to play and win. Boiling it down to non stop brawling like league or any other soulless moba.