Every physical card game from Magic the Gathering, to Yu-Gi-Oh, to Pokemon is more "P2W" than Hearthstone. And there isn't anything wrong with those games. It's an established business model. Diablo Immortal is a completely different game and comparing the monetization is apples to oranges.
In DI if there are enough players on your server paying to win, you can never compete for immortal as a F2P, period. Even if you're mechanically the best player in the world and play 18 hours a day. That is never the case in hearthstone, it doesn't matter how many other people are buying packs in hearthstone, once your deck is built it comes down to your dedication and game knowledge to reach legend. Yes you can get to that point slightly faster if you pay, but its on the same level as buying a level boost in WoW so you can reach endgame and do arenas on a new class. The cap is very low by comparison, and reachable without paying. It is not a pay wall.
Hearthstone caps out once you have the cards for a deck, you can't grind or pay for any further advantages. This cap only changes when new sets come out or cards are re-balanced, basically when the meta shifts. A person who bought every single card in hearthstone isn't anymore likely to win than someone who played for free and earned enough to build a single complete meta deck.
Meanwhile you can dump $500,000 into DI and have a stat advantage over anyone who spent less on the game. Your $500k build is strictly better than someones $300k build regardless of skill. A free player will always be capped by time because reaching the max (Comparable to having a full deck in hearthstone) will take longer than the game is probably going to be live, on the order of decades. Where a paying player is virtually uncapped and will always have the stat advantage.
These are nothing alike, being alright with one and not the other doesn't make someone a hypocrite.
Honestly worse than HS because the "arena exclusive" cards often have the same name and artwork as existing cards from the physical card game but with completely different effects. Way too confusing for anyone that plays both. Not to mention having cards that literally have
293 words of rules text.