If it doesn't handle the card rules automatically for you, then it's way worse than MTG Arena or MTGO. I've played with free MTG software (cockatrice) and it's not close to the same thing, even though it has all the art and buttons for doing all the effects manually (I use this shortcut to draw 3 cards, this shortcut to put 2 back, this shortcut to exile someone's graveyard, etc).
If they really built the best site for playing MTG, even over paid versions, then there's no real way to hide the fact that it's magic-specific.
I'm not competing with Arena. Arena has a rules engine and great graphics. But Arena has a tonnnn of limitations and does not let you simply "build any deck you want and play with any number of friends in any format you choose." For what Arena is meant to do, Arena is better. That was never my goal.
I'm competing with Untap.in and Cockatrice, and what I built is just a much, much nicer version of those things. If you give me your email, I'll send you a link to it and you can try it out yourself if you'd like.
If they really built the best site for playing MTG, even over paid versions, then there's no real way to hide the fact that it's magic-specific.