I hate pay-to-win, and indeed constructed HS has a degree of pay-to-win until you have a decent amount of cards. If arena didn't exist, I probably would have quit. Instead, I played hundreds of arena matches, playing a bit of constructed here and there when I needed gold for the next arena fee. That got me a card collection sufficient to build 3+ good constructed decks, and I didn't even disenchant any cards I didn't have duplicates of, which would have sped up the process (at the cost of slowing down later deckbuilding).It's also just not that much fun. That's good feedback that says to me to skip it.
The same would apply to Magic the Gathering - if both players have similar quality cards, it's fun, if one has a clear advantage, I don't think so.
Now, if it had play segregated to 'free players' could only play others with similar cards, that'd be fine, but it doesn't sound like it. Sounds 'pay to win'.
For a free player who doesn't have cards for good decks yet, arena is nice because there's no pay-to-win aspect to it, and you eventually get to experiment with every card over the course of playing multiple arenas. Even if you have a good constructed deck or several, arena can be an interesting side dish because it takes slightly different skills and mentality. If you play well, it gives you more cards/dust over time than playing constructed and buying packs with gold. Play really well, and you get more gold from each round than the entry fee was, so you can buy into a new arena without having to go pop in constructed at all. (That level takes quite a bit of skill though.)
I'd recommend playing a bit of constructed with cheap decks first to get a feel for the game mechanics and get familiar with the cards. Newbie mistakes are inevitable, best to make the first bunch of them in casual mode where they cost nothing instead of in arena where they prematurely end your arena run.