Everyone is of course right when they say presets as a starting point is a good idea. DAW tools such as EQ and Compression are generally very good, especially in something like Logic Pro X and updated versions of Cubase.
One of the biggest issues most people have is the end product. Anyone can write a track, but it’s a lot more difficult to get it to sound good. That’s where a lot of the rejections come from imo.
Some of the compression I see on the tracks submitted here make me cringe. I can’t believe the amount of compression and limiting that gets used in a lot of these tracks. They don’t get rejected necessarily, but they sound like s**t most of the time. EQ on the other hand should really be used most commonly, but not always, to reduce.
It then boils down to what kind of sound you like to come from your plugins. If you can’t get a good result from DAW plugins, it’s highly unlikely that expensive 3rd party plugins will make any difference either.