Using the Dutch Defense as a low-rated player

At the moment of writing this post, I am a 900 ELO-rated player who tries to play the Dutch Defense when given the opportunity as an offbeat opening. My main problem is that people who are similarly rated to me don't play around with the traditional opening theory behind the Dutch; instead opting more central bishop development (not Fianchetto-ing) or developing knights. I was curious if anyone had some ideas for how I can counter secondary/uncommon lines of the Dutch Defense at a beginner level. Thank you in advance.

You should not be studying openings at your level and you just confirmed it yourself. You need to UNDERSTAND, NOT MEMORIZE openings. If you understood it, you would easily be able to answer your own questions of what to do when they don't fianchetto the King's Bishop. But you can't because you aren't ready for that stage in chess preparation.

At your level, you need to study endgames, and before you say you know your endgames, can you:

1) Demonstrate what Lucena's position is and how to win it?

2) Demonstrate what Philidor's draw is and how to execute it?

3) Demonstrate what the Short Side Defense is and when can you use it?

4) Demonstrate what the Passive Defense is and when can you use it?

5) Demonstrate what the Vancura Position is and when and how to execute it?

6) Mate with a Bishop and Knight vs Lone King with 2 minutes on the clock and a max of 50 moves?

7) Can you even identify SPECIFICALLY what ending items 1 through 5 above apply to? What is all the of material that is on the board in those first 5?

Tactics - Do you know what each and every one of the following are?

1) Relative Pin

2) Absolute Pin

3) Fork

4) Skewer

5) Interference

6) Deflection

7) X-Ray

8) Zugzwang

Positional Understanding:

1) In the Stonewall Dutch, what is Black's biggest weakness?

Openings should not be your focus right now.

Yet you do have to make a move on move 1

I’m assuming you’re seeing stuff like 1. d4 f5 2. Nc3 or 2. Bf4? I don’t know off the top of my head but I’d probably recommend just developing your pieces to nice squares, castling, and then playing an equal or better middlegame, as White isn’t developing optimally.

i dont see what the problem is. You are at a level where no one even knows what a dutch is, so they will just develop pieces. You find a preferred formation as black within black for such piece play and play chess.
ignore thriller's insane endgame recommendation. almost No one knows any endgames until the latter half of the 1000's beyond basic pawn promotion ideas and rook basics. i ccertainly didnt know half of what he listed until i was over 2000. (they are literrally IM + players that dont even know what the Vancura is!)
play an opening with sense, do your puzzles,, watch games, there is so much to absorb when you are 900 you almost cant go wrong on what you do (except geek out on endgammes when you blunder pieces lmao)

LOL - you are also 2000 while the OP is 1000.

If you were the author of the original post, my response would be different as I would assume you know those, or at minimum the Lucena and Philidor.