Having played through almost all of PvZ2, I can say that the Free to Play BS doesn't ever get to the level where I felt the need to spend money. I'm sure that I could have made my playthrough much easier if I had spent money, but I enjoyed the difficulty of the game having not spent any money.
The coin currency to buy plant food/instakill skill is more than plentiful enough to use it when you get in an "OH S#$%" moment without ever needing to buy anymore. The keys that drop to unlock gates is pretty rare, but by the time I beat all the levels in the initial two zones, I had earned more keys than needed to unlock everything. I had to replay some levels a few times because I didn't spend coins when I could have, but I lost to levels in PvZ1 sometimes as well when I didn't plan ahead far enough.
If the Free to Play crap bothers you, then don't pay them anything. Enjoy a difficult but very fun game and pretend that the microtransaction stuff doesn't exist. I will whole-heartedly recommend this game to anyone who asks.