I'm sorry to hear of the issues your encountering with your phone @Disappointed_
I had some issues with my Samsung Keyboard which I resolved by fully resetting the Keyboard within it's settings.
It now works flawlessly for me.
Can you try Safe Mode just to see if anything downloaded onto the phone is causing conflict.
Safe Mode > https://www.samsung.com/uk/support/mobile-devices/how-to-start-my-galaxy-device-in-safe-mode/ turns off downloaded apps and themes etc which may highlight an app or theme that's causing conflict.
Also consider trying > Clear Cache Files from the phone's System Partition Section > https://www.samsung.com/uk/support/mobile-devices/how-do-i-clear-the-cache-on-my-device/ You may need to insert your earphones or hook upto a powered On Laptop to access the Clear Partition Section. This may help with lag or stutters as this clears the phone of old/unused or broken cache files.There is also a Repair Apps option in the Menu System too.
These are good sound troubleshooting.
There is also a Diagnostic Tool in your Samsung Members app that you can run just to check the phone itself.
For me I find the Twitter App OK but when scrolling it can stutter.
Twitter via my Browser Url is a much better experience.
It might be beneficial to clear the cache in the apps affected which is performed via Settings > Apps > Choose the app from the list > Storage > Clear Cache > If absolutely there is a clear Data option as a last resort.
I appreciate you've lost faith in the product but I only mention the above options to try and help you.
If I can be of any further help then please don't hesitate. Take care. 😎
Daily Driver > Samsung Galaxy s²³ Ultra 512Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "
