The more that is given free, and the more and better the playtime, the more I feel well-treated, and the more I am likely to (and do) spend. Recently especially there's been a lot more free toons and advance warning as to what was needed to get them, and they've been very usable and interesting even at lower stars. I'm in top 100 on a 2015 shard with the Rex/Chaze/Zylo/DN team, and only two are 7*. And all were acquired through F2P (though since I do the monthly crystal subscription I'm P2P even without the occasional May 4th etc. bonus crystal purchase).
And all toons, and all currency (i.e. including crystals) is easily acquired through F2P, it's not like some games where there's a premium currency only available for cash.
And as frustrating as GW sometimes is, it is enjoyable to me to figure out how to defeat a team with no (or acceptable) losses, and the time taken is fun, play time. I like that I can't reliably auto GW or arena or ships, because it means I think, and play, don't just hit auto. And because they're different each time - credit heist or challenges being the same, I wouldn't want to have to play through them all again.