It's never felt unfair or a grind to me, and this is coming from someone that quit Runescape in under an hour because things weren't happening fast enough.

It isn't that big of a deal unless you want to start playing ranked games, because the bigger pool of champs you have, it helps with counterpicking, trading with other teammates during draft and learning counters to champs.

I played LoL for about 2 years and after having 1,200 matches I only had about half the hero pool with only having bought maybe 2-3 champs.

So in the competitive scene for LoL, it  definitely feels like pay to win.

Thats the only reason I tried out Dota 2, because the hero pool is available from the start so I can try out every hero and decide which ones I like.

I really can't tell what could be the right way, but I definitely can tell two ways to avoid like the plague:

1) Zynga way: crappy or repetitive games that trigger and exploit obsessive-compulsive behaviours
2) EA way: ruining games that could even be very good with a bad transaction system (spending almost all the rarest and hardest earned kind of game currency, very slow to earn playing, expensive to buy with real money, by mistake, hitting the wrong button and not being asked for confirmation, made me hate Real Racing 3, that I quite liked despite some flaws, so much that I stopped playing it altogether. I'm still mad with EA for the time lost, and had I spent money for that game gold, I'd be even madder. Surely after this experience, even if I'll eventually forgive EA, I won't trust it anymore on its F2P games.

Pretty much this.