I am a 1900 (approximately) and still get depressed every time my white opponent opens with 1.d4. I just don't seem to find my way with this opening. Currently i play nimzo and QID but both are quite heavy on theory and nimzo just gets very sad if white goes for Bd2. I prefer solid positions, for instance I really enjoy play caro-kann or french against 1.e4.. So what defence against 1.d4 you think I'd enjoy? Thanks.
Try the Dutch Stonewall. If you are a French player, you can play the move order 1. d4 e6. After 2. e4 you have a French, after 2. c4 f5 you are in a dutch, avoiding the staunton gambit (not a problem in its own, but if you prefer solid play ...)
After that, with a stonewall setup you have a solid middlegame, albeit a little passive
PS: I am 1900 too.
Play the Chigorin! I went from 1900 to 2000 FIDE playing it. A good book is play 1...Nc6 by Christoph Wisnewski. Good luck.
Nimzo and QID are two of the most highly respected and powerful responses to 1.d4 the Nimzo has always been seen as the tough nut to 1.d4 and it was said that people played 1.e4 so they wouldn't have to face the Nimzo! The theory in both are quite heavy yes but it's not unmanageable and you would be in good company as well playing these two openings as they have all been championed by multiple world champions from the past and present.The move Bd2 in the Nimzo (assuming in response to 3...Bb4 ?)is just considered bad for white as the Bishop is misplaced on d2 and black gains good control over e4 after castles and b6. Please just don't abandon openings as rich as these as they provide a great learning tool and exposes you to a multitude of positionally as well as tactically rich positions.
Slav is considered super solid but be aware that white can achieve a relatively easy draw via exchanging on d5 after 2...c6,
Another point behind the Nimzo is that it provides chances for a win and produces double-edged positions with chances for both sides.