I had a Nexus 7 (2012) that was barely ever used. Even that became comically slow as dirt. Was really an eye-opener about how bad a lack of attention from a vendor can be. They'd moved onto the next thing and evidently did not care one iota.

The original model (2012) was pretty terrible as you mention.

The 2013 (with rear facing camera) is still more than usable. I'm more than happy and have bought several over the years. (Rough environments, but £50 used on ebay is doable)

I have that last model of Nexus 7 and it still works wonderfully. I love that thing to death. If it had SD slot, it would be perfect. However, there's OTG - so, until it breaks it's wonderful.

Yes, it slows down quite a bit (2012 model), but it still is the best tablet I've seen.

I don't want any manufacturer "features" on Android, I just want a pure Android experience. And also looking for a replacement for my parents aging Nexus 7.

They are still working perfectly. I haven't heard any complaints. My parents are probably nowhere close to filling up the storage, though.