There are a number of contributing factors that i can think of:

* Room sound. A remarkable-sounding room cannot be emulated. And a bad-sounding room cannot be removed from a recording. It's always best to consider the recording process from the beginning.

* Quality of gear, especially mics and pre-amps. Lower end mics sounds very uneven and sometimes metallic. And lower end pre-amps don't have the nuance that better ones do.

* Mic placement. Having a good room and quality gear doesn't mean the recordings will all mesh well together. A good engineer will know which mics to use and where to place them in order make the mix best/easiest.

There's lots more, but those are the three items that stand out most to me.

As a general principle (meaning, one to be broken a lot, but a good starting point), if you're finding yourself using a lot of EQ to try to simulate "professional" recordings, particularly trying to avoid that abrasion, you're recording the thing wrong to begin with. Everything Jory said - room acoustics, mic position (also: mic selection).

People often underestimate the extent to which musicians impart the sound you hear on finished albums. Recording a great guitarist with a really good instrument, regardless of recording equipment, will produce such a different result than recording an amateur who doesn't know how to perform for a recording. To give an example: I've recorded a lot of darbukka/doumbek players here (the US) and in Turkey. I've recorded fairly well-known players here in the US in good studios with great mics that ended up sounding mushy, thin, and a bit abrasive, and in the mix I had to EQ, compress, reverb, re-compress, and EQ again the sound to get something usable. I've recorded incredible studio musicians in Istanbul with crappy mics and an awful room and the sound was perfect - no EQ, no compression, no reverb required. In this case it had everything to do with the player. The Turkish studio musician had a style that recorded well. Few American players of that instrument have developed such a style.