Big issues they haven't solved for years:
- The mobile app has many issues, UI bugs and generally doesn't serve it's purpose.
- The support either has you wait for 3 months+ (this is true with multiple of my friends) or just marks a ticket as solved even though it is far from solved, ignoring your actual issue.
- They don't know which features the community wants, leading to updates that were not thought about enough instead of improvements to per example the permission system.

Edit: Most of these got resolved or are no longer an issue due to other changes made.