EQ is a tool that you should use to get clarity and separation.
If instruments are competing for the same frequency range, then EQ can help make them sit well together.
A nice cut in a less important instrument in that frequency range can go a long way to free up space for others.
If you have no idea how to EQ effectively, the simplest and safest thing you can do is to use a High Pass Filter.
The low end of your mix should be occupied by the bass and drums. The other instruments do not have a lot of information in the low end, but they have some that might add up and make your mix sound muddy if you’re not careful.