It seems we have some fundamental differences in opinion here. I don't think it's pissing in anybody's face for a full time dev to make money off a free offering of their product. The app has never had ads for me since I block them at the DNS level. I still paid for it to support an app that's going to dominate my screen on time just like it did on Reddit.
Like you said, the rest of the apps don't currently have ads. A lot of their devs also said they'd never have them. That's great for them. I don't how many of them do this at a full time job either. Or how long they'll continue to support their apps under their current models (aside from Jerboa which is developed by one of the Lemmy devs)
It would be great if Sync could rely only on donos, but the amount of people bitching about a one time $20 purchase being too expensive or expecting to transfer their $1 purchase of Sync for Reddit 9 years ago to Lemmy has me thinking that's just a pipe dream.
If it's not worth it to you go ahead and use a different app. It's still not pissing in anybody's face no matter how much you don't like it.
I get that. A lot of the differences are only going to be evident as you continue to use the app. If you're already set with Thunder then that's great and I'd encourage you to donate to the dev.
If the ads in Sync aren't an immediate turn off/deal breaker I'd also highly encourage you to give it a real shot over a week or so. There's a bunch of customization options to tweak it just how you like and the app runs smooth as butter, for me anyway. The app was super popular on Reddit for a reason.