The 4...Nbd7 move order in the QGD may be a good option.  Also regarding the Exchange, Black might strongly consider playing 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.cd Nxd5.

There are many answers to the original question, and you might want to look through some of the older threads around here asking the same basic thing.  The Schlecter Slav is a fine suggestion, as is the Queen's Gambit Declined (various options here), Czech Benoni, Stonewall Dutch, some other slightly offbeat Slav lines, some Nimzo-Indian lines...you can play all of those with a general knowledge of plans and ideas, and lack of "theoretical" knowledge is not likely to have you blown off of the board.

How about keeping the dutch, and keep playing through the 1...e6 route?

Not everyone you face will transpose to a french, so you will normally get that opening. You can keep the french in your repertoire as a back up to 1..e5 if you still plan on using that as your main defence against 1.e4.

If you can wait a few months, Ntrilis's Play 1.d4 d5 book may be exactly what you need.  It's QGD-based, covers the sidelines, and promises to explain the ideas and plans.

Monocle, you may not like to hear this, but I think you are the only person who can answer your own question.  Let me explain why I say that.  At a 1900 level, your opening choice is not that critical and just about any opening could work for you.  So how do you pick?  I believe you have to pick one that is most comfortable for you if you want to reduce your workload and lack a good memory.  What do I mean by comfortable?  It's an opening where you have some understanding of the typical plans and pawn structures so finding the right move comes more natural to you.  How do I find out which openings are most comfortable to me?  Get a premium subscription to ChessPublishing, play over the games in the 1.d4 section and find out which ones you can guess the right move a greater percentage of the time.  Then look at the GM/IM annotations and see where the critical positions are and see if you can follow the plans and ideas they recommend.  Then pick an opening and don't look back (stick with your choice at least a year or more) and see how it goes.

We can all make suggestions but the only way you will get a good answer is to try things out yourself.  For example, in my case the King's Indian seems to come naturally to me and although it has tons of theory, I seem to understand it and can find the right move more easily even if I can't always remember it.

I hope that helps.

I guess I could try the Czech Benoni against 1.d4 Nf6 2.c4, and the Bogo against 1.d4 Nf6 2.Nf3 e6 3.c4.  I wonder if anyone has played that combo before...

I know with the QGD I could also avoid the Nge2 exchange with 1.d4 d5 2.c4 e6 3.Nc3 Be7, and I could avoid the 5.Bf4 variation with 1.d4 d5 2.c4 e6 3.Nc3 Nf6 4.Nf3 a6, but I haven't yet found a low-theory way to avoid both.  The exchange is more common, but I find the 5.Bf4 stuff much more difficult to face. 

Earlier this year, I started playing again after a decade of inactivity and I'm struggling to decide what to play as Black against 1.d4.  I have a terrible memory for concrete variations if I don't play them very often (and even then I struggle to remember anything after move 10 or so), so I'm trying to find something solid that is not too theory-heavy or concrete, and avoids early simplification and keeps at least a bit of tension or complexity so that there's scope to gradually outplay slightly weaker opponents.   

I'm not looking to counter attack from move one or provoke wild complications to avoid draws at all costs, and I'm not too worried about White getting a theoretical += if Black has clear plans that don't involve just sitting tight or swapping all the pieces off for a draw.  Really, I just want to keep the pieces on and have interesting pawn structures and not have to walk an early tightrope where one memory slip is fatal, but I don't know if that's too much to expect with Black.

Years ago, before my break from chess, I used to play the French against 1.e4 and the Dutch Stonewall against 1.d4 via a 1..e6 move order.  The stonewall met my needs quite well and I had good results with it, but the French never really worked for me - I didn't like the locked pawn chains, and I struggled to beat lower rated opponents in the exchange variation (which I also found rather boring).  I gave up the French, and after a few Sicilian experiments went back to 1.e4 e5, but then I had trouble playing the Dutch via the 1...f5 move order.  Instead of stonewalls, I was mostly faced with a bunch of sidelines that always led to wacky positions where I had no idea what was going on and didn't much enjoy playing.  So I abandoned the Dutch, but never found a replacement.

I haven't played enough rated games to get a new ECF grade yet, but I'd guess I'm around 160-170ish, so something like 1900-2000 FIDE.  Ideally, I'd like to improve, but I fear my inability to learn concrete variations will hold me back.  I'm somewhat jealous of people who can have multiple openings in their repertoire or play a range of sidelines, because honestly, I find it a difficult task to fit just one narrow repertoire in my head.

I've been looking at the Old Indian, Benko, KID with Nbd7 (via OI move order), and Slav sidelines like 5...Na6, but I'm not sure about any of those as they aren't often played at higher levels.  The QGD Tartakower would be great, but I can't find anything I like against the 5.Bf4 variation and Nge2 exchange variation, which I'd get way more often if I took up the QGD.

Any suggestions?  What do theory-averse 1900+ rated people here play as black against 1.d4, when they want a solid but interesting game?