Are Preamplifier’s Relevant Today or just a Hinderance with Digital Playback ?

I suppose it could depend on how many sources. I have no use for a preamp. 

If you're basically using a computer as a source to headphone amp/dac I can see why it would be heavily against a preamp. Why add extra components?

You don't know what the "colorations" are. You're getting into what Floyd Toole called the circle of confusion. Take the mic, room, equipment,  speakers etc.. used to record and these Recordings are as different as night and day from each other and whatever you're using to playback with. There's no way to recreate the thousands of different combinations to get what the final mixers heard. It's a waste of time trying to tune your system to a live event or certain recordings the best you can do IMO is reproduce what's on the media as neutral as possible, use as transparent gear as you can possibly get. That's simply what I do. There is no right or wrong way,  take whatever approach gives you the sound you enjoy with what you can afford.