For the first time ever on this forum, I actually agree with you - sort of.
It's important to not compromise too much of what you already have in the track. But, it's also important to ensure that there is room for vocals. So, yes, you are right: try cutting/dropping some db of some popularly used frequency ranges in the track. This will allow for your vocals to overtake them, and thus, have a higher presence within the mix.
Place a *graphic*equalizer on your master channel/bus and then, play your track. (If you don't have a graphic EQ, find one. If you're using FLStudio, the Fruity parametric EQ 2 is a graphic one.) Now, as the track plays, you'll notice that the graphic EQ will start lighting up, highlighting all the major frequencies that are being most used in your track. Use this merely as a reference to know which frequencies you should lower within your track.
Now, hunt down some of those bad boys and cut/lower some of their Db with an EQ. This will help free up space in the mix for your vocals. If it doesn't sound as good as before, don't worry, the vocals should help compensate later on.
Add your vocals back in the mix. Use an EQ on the vocals and boost in the range of the frequency/frequencies you just cut from other audio in the mix. If they still don't fit, EQ the vocals a bit more. They say you generally shouldn't compress vocals, but use some compression gain to compensate for volume to ensure it's slightly louder in the mix.
Hope this helped