I think a lot of the developers that make these games have learnt some lessons over the years, you can play most gacha games entirely f2p without issue.
Buying stuff just speeds up things, sometimes by quite a lot, depends how deep your credit card goes.
It's rare to have things truly gated behind paying, normally it's just paying = faster to progress, and in the case of limited characters or skins, it can be fomo where not spending means you can just miss out on things entirely, that is certainly one way they will try and trap you in.
Saying that, I don't mind spending a bit to support games I like but I prefer it when the game itself is also kind of generous with rewards and events, it makes me more inclined to contribute into the game if I am met part way there.
Ultimately though - they want your money 
If the game doesn't unlock all the things you need to play and gates some of it behind summoning then it's very much in the traditional gacha sphere.
Exactly! I don't super obsess over it or theory craft into oblivion but I still want my teams to be effective as being able to do the challenges is fun to me, and is one of the reasons I like to build my units up. Some units have good pairings so useful to discuss them sometimes I find.
