the etb effects make me feel like counterspell should be in standard.
Some counters do see play, and I run things like Make Disappear as well as Ertai. The problem is they kind of janky and slow, which makes them feel like dead cards way too often as the conditions just don't line up or they can outvalue them.
Yeah, that's part of the problem. If you have a choice of building around Invoke Despair or something janky like Bard Class you spend the same amount of rares either way so you pick the straightforward card every time. Whereas IRL cards like Bard Class are sub 50 cents because way more people open them then want them.
The other thing is I just won't pay money into Arena, whereas I didn't mind buying real cards. Even if a card loses it's value post rotation, I still have it and can do whatever I want with it, but if Arena just fucks with a format, such as forcing Alchemy into something, there's nothing you can do about it. Hell if they just decide to ban you for some retarded reason, then fuck you, no refunds.
And don't forget, they've just removed cards for being racist or sexual, so what happens if a card from a modern set ends up having a controversial artist? I'm guessing they'll rip it from your collection, or just change it, as Hearthstone has changed things like "Succubus" into a Felhound to appease Chinese markets.
Black removal is as strong as it's ever been. It's really just the other colors that are in shit city, except maybe green (1 mana fight spells are mostly interchangeable) and blue (almost never has a real answer to resolved permanents anyway).
Black removal is strong, but it's been made weaker because of how much recursion there is. There are just so many cards that pop out of the graveyard, or bring things back from the graveyard, have ward, or simply negate removal spells that even something like the 2 mana kill any creature and lose 2 life feels clunky. Then there's the Planeswalker issue, that a lot of the time if you want something that answers those things you have to have a really inefficient spell.
It's why Leyline of Binding is as popular as you mentioned, it just hits anything and exiles it, though it can be removed as well. The 5 mana black spell that goes down in cost for each dude in the graveyard but exiles the creature is seeing some play as a result.