I'm having a consistent problem when trying to use custom GTK themes in Ubuntu, as well as Linux Mint.
For every theme that I try, the padding on the menu buttons is gone, except for in the default theme, and there are areas where widgets are "too close together".
Here are examples of what I mean:
Ubuntu with the United-Ubuntu theme:
Linux Mint, also with the United-Ubuntu theme, same problem:
Ubuntu with the Vimix theme:
I usually just search for an answer from the internet for all of my Linux problems, but this is a special case where I cannot find anything on this whatsoever - I seem to be the only person with this sort of problem.
I'm guessing it's not a consistent design choice - is there something wrong with my setup? Do I need to update my software? Will I need to edit the .css files myself?
Any general steps in the right direction will be highly appreciated - it would make finding and using custom themes a treat instead of a chore!
Ubuntu Version: 16.04 LTS
Linux Mint Version: 18.3 Cinnamon
Both of the above screenshots were taken after installing, and after running sudo apt-get update and sudo apt-get upgrade.