My coworker who got me playing Arena has been playing since the 90s and said he hates them. I can see how they sorta ruin the "pure" nature of the game.
Grandpas complaining about planeswalkers! That's my jam!
I dislike them and have always disliked them because they often incorporate a value engine, board control element and win condition together in to a single card. Jace the Mind Sculptor and Teferi Hero of Dominaria epitomize that form of one stop shop. Thing stayed on the board a couple turns and the game is over. Bleh. Planeswalkers have eaten up some design space that would previously have been occupied by artifacts and enchantments. That's gotten worse now that different static ability walkers have been made. Saheeli Sublime Artificer, Narset Parter of Veils and Teferi Time Raveler are really good examples of that.
Since their addition to the game the planeswalker card time has been the beneficiary of three different global buffs. The legend rule was changed to allow both players to have the same legend in play and thus the same walker. Each player can have multiples of the same named walker provide it is a differently named version. Lastly they changed how planeswalkers are damaged. It used to be that whenever you did noncombat damage to a walker from ANY source you could choose to redirect it to a walker. Now the card must say that it can damage any target or walkers specifically. This resulted in many cards that could previously tag a walker now being of no use against them.
They routinely shit up limited formats. Setting aside power that is due in part to answers to planeswalkers being rare or mythic. Your draft-tier removal spell probably can't do shit. This is tied to something small that really rustles my jimmies - the Murder that hits walkers is a rare and they've made that fucking card again and again. You crack/buy/trade for Heroes Downfall and then that rotates out and you have to get your Ruinous Path than your Vraska's Contempt then Murderous Rider. It's the same fucking card. It's Murder + Set Flavor and the value drops through the floor every rotation.
I don't like how limited to nonexistent punishes to planeswalkers are. Where's my Ravenous Chupacabra that eats walkers. Where's my counterspell/stifle that eats a walker if it counters an activated ability or Cancel + Quash that exiles all walkers of the name from the opposing player's deck and hand. When a walker is played it almost always does a thing for value while forcing the opponent to devote some amount of resources to removing it. I want something that makes playing a walker feel at least a little bad. Getting hit with a Smash to Smithereens or Searing Blood
feels bad.
Oko is a fuck because of how much loyalty he has for a three mana walker with two plusses. Walkers are at their weakest when their controller is behind on board but he's so fucking cheap and fat. He's going heavily dictate what kind of aggressive strategies can even exist. Field of the Dead makes traditional control shitty even though counterspells are typically super good versus ramp. The core set should always have some basic meat and potatoes answers to card types so you don't get in to a situation where you have to emergency ban a land that makes a fucking 2/2 on landfall if you have at least seven different land names. Christ that's embarrassing. Between Oko and Field you're looking at a battlecruiser format where both sides are fucking off for most of the game until we see who can do the bigger, dumber thing and win off it.
1. People getting sick of walkers
2. Have answers in your core set to basic shit like nonbasic lands so you don't look like chumps
3. This was one long rambly post