They're a huge company, they could easily acquire five of the third party apps, add ads and keep the developers on payroll to maintain the apps. Banning apps that don't show ads of course.
I use Boost because it's far superior to the Reddit app and to Reddit's website (even old.reddit.com), despite Boost having ads and despite me being able to avoid ads on Reddit due to having an ad blocker.
So at least for me, using a third-party app is well worth it despite seeing ads.
I have leared to ignore any promoted content i.e. ads in my reddit timeline, mostly because they are irrelevant. The app is regardless slow as hell. The Dawn app in comprasion, is extremely smooth and a pleasure to use. I'd guess the difference is the amount of tracking and analytics the official app is trying to do, I'd guess it is also not a native app.