I rarely preorder games, but not because I have something against the preorder specifically, or am trying to 'boycott' them. It's just that there aren't many that interest me. I will pre order games I think I will like and specifically want to play on release, as otherwise I'd be buying it on launch anyway. There is no reason for me to not get any bonus items, and be able to preload the game, in that case. The only time I've been 'burned' on a preorder was probably Cyberpunk, but even then I got a good amount of playtime out of it, it just wasn't the RPG I was expecting (not an RPG at all).
A game like this it's a bit different. As this is an ongoing MMO, it's kind of a necessity to buy the next expansion(s) regardless of whether they are good or not - I mean if you want to actually play it seriously. Granted, you could wait for a sale, but you'd still be inevitably buying it sooner or later anyway. I typically go overboard and get all the digital collector's editions, plus now I typically preorder. I think I missed the Stormblood preorder, but I'm pretty sure that came out during a period where I didn't have any access to internet altogether (other than phone) and was moving from place to place. Also, you can have them charge the preorder instead of waiting.
I've used a lot of fantasias, but I can proudly say I have never even thought to switch to a lalafell. I've had that feeling.. I will obsess over how much I spent, and probably gave myself anxiety attacks over my impulse buying problem. I have routinely wasted money on fantasias, hundreds of dollars worth at least. I'll obsess over some small detail that will make it a 'no go' for me, and require another fantasia. Now, I've just been trying to stop buying them altogether this year. Haven't bought one since June or so when I switched back to au ra (after saying prior I was gonna stop using them). Those are an actual waste of money. Now outfits.. I can get behind that. Those consist of actual items you can use, and even find new uses for as new items come out.