So, there's not just one problem with Artifact.

First, the game isn't free. This isn't what you seem to think it means. Magic isn't free, but Hearthstone is. Magic Arena is. TES legends is. Gwent is. Artifact... isn't. You cannot try the game for free. If you want to find out if you even like Artifact, you have to shell out $20 which is more than a Hearthstone starter pack and you can find out if you like Hearthstone first.

Second, the game is very heavy on the microtransactions. I know this sounds like nothing new under the sun for digital CCGs, but holy hell is Artifact the worst offender by far. There's been several reports by streamers/youtubers who spent several hundreds of dollars on packs and didn't even come close to building the decks they wanted. By converse, in hearthstone, spending $300 on packs back when there was only one set was basically a guarantee of being able to pull/craft every card in the game.

Subpoint: You can pull Sven from card packs even though every player gets him in the starter pack. What's even the point of that? The devs clearly just didn't think this game through. Basically, the value for your money is really bad.

Third, in this small community of players, many are nearly a full year ahead of you in play experience because they took part in the play testing phases if you just started on launch. This doesn't sound that bad, and it sort of isn't, but if you're a serious player it's incredibly polarizing.

Long story short, you have a game that has a poor community because there's no f2p segment, you don't even get a good experience for what you play for, and you only find out about all of this after it's too late.

This is why you've been hearing so many bad things about it. Because it's not good and people are trying to warn others before they spend money finding out for themselves.