I don't think that EQing before recording is bad, it does beat the purpose of the digital recording flexibility but even changing a microphone is -in a way- EQing.
If you have an EQ and an EQ setting that does justice to the guitar sound i don't find anything weird or bad about EQing before the recording stage!
The thing i would address though is the actual sound and the way it's recorded that makes you think is "thin"
Most people nowadays think , record and mix later i believe that the sound/signal recorded in to any medium (DAW for instance) must be very healthy and promissing otherwise you'll just end up circling around the same bad initial sound.
So one or two things that can make a guitar sound thin
1.If you are using double mic setup always care about phase!
2.Try going towards the ring of the amp speaker to get more body
3.Use microphones with larger diaphragms dynamic or condenser.
Mixing and recording is a series of decisions afterall , so i don't find anything bad about EQing before you go in your DAW but i feel that your problem lies elsewhere.
You might want to go deeper in guitar recording techniques and different microphone setups , also ribbon mics tend to capture the tight bottom end of the guitar amp.