Didn't even know what a 3rd party app was until the protests (never used reddit on my phone to limit the amount of time spent there, and was never very tech savvy).
Left because of other reasons, like a couple mods of communities I love packing up and leaving and the sheer principle of it all.
Did you use reddit with reddit enhancement suite on desktop? I ask because I found reddit was such a terrible experience without being able to block off a bunch of stuff beyond what reddit offers you in their settings.
Felt like the longer people used reddit the more they ended up seeking out stuff like third party apps or extensions like RES as the feed started changing over the years of what got promoted.
I would have used reddit so much less without those or started avoiding it even if there hadn't been any api controversy.
Im a very simple person, and used reddit for very specific things. I didn't even check my notifications, and participated on some not very big communities. Didn't even browse the main feed, just opened some tabs with the few subs I wanted to check out, got caught up with the new content that day and moved on to the next tab.
I know Im very much not how the average person interacts with the website.