There are lot of basic problem with os but they refuse to improve,  some mentioned below.

1) Cursor mover ~ worst ever, nearly useless. they should learn from MIUI

2)Contact icon on home

3)Music player song search

4)No local temporary pop up audio player,  each audio file open music player

5)No Volte

6)No ota update

7)No document reader

8)No Selection of Sim calling

9)Messy log, No simplicity. No clear uniform distinguish between time, day

and many more which have raised but no action. Add more you faced