Denial

Bought a vga converter to connect my Vic to an LCD monitor. It looks terrible.

I adjusted the pot according to the wiki (this is a cost-reduced Vic so only one pot) and it makes it brighter but that's it.
Is it because my vga converter is crappy?

try POKE36864,133

... but generally, I would say yes.

Most of the Chinese converters stink unfortunately. I bought an older 20" LCD TV for $15 just for my retro use and it works good. There are some converters that work but they are usually more expensive. I have 3 of these because they work good https://www.ebay.com/i/172015299322?chn=ps (shop for the lowest price). Its hard to find them new anymore. Just make sure it comes with a remote and cables. I have tested them with all my retro systems and game consoles.