If your 3DS is on 11.0.0-33 firmware, you need a hard-mod or a replacement, to install a9LH and/or Downgrade to 9.2.0-20. End of story.
Yes, you can *barely* launch Homebrew on 11.0.0-33, but not everything will function as intended, including but not limited to; DOWNGRADING
Here's an explanation of why your 3DS isn't downgrade-able:
The 3DS consists of 2 CPU's;
The ARM9 CPU, which deals with Security, Encryption, Validation, etc.
The ARM11 CPU, which deals with Executing and Running Games.
The 11.0.0-33U firmware has patched all of the ARM9 exploits available at the moment, and patched most ARM11 exploits.
A limited amount of ARM11 exploits (Homebrew Launching) still work *mostly* in 11.0.0-33U firmware, including Freakyhax and SmashBrosHax.
In order to gain the ability to exploit the ARM9 CPU, the following would have to be done:
1. Hard Mod your 3DS, so its NAND can be Read/Written by a computer (preferably Windows). Many trusted people worldwide, on GBATemp, offer NAND Mod services (sometimes paired up with downgrading):
https://gbatemp.net/threads/list-of-hardmod-installers-by-region.414224/
2. Read the NAND, and modify its 11.0.0-33U firmware in order to downgrade it:
https://github.com/Plailect/Guide/wiki/Hardmod-Downgrade
3. Write the downgraded NAND copy to your 3DS's NAND, and your 3DS is now partially downgraded, but enough to be able to go ahead with the next step.
4. Due to the fact that the 3DS's NATIVE_FIRM is downgraded, you are now able to fully exploit the ARM11 CPU, which means that you can downgrade even more (which is necessary).
5. Due to the fact that the ARM9 CPU exploits were patched after 9.2.0-20U, you must downgrade your now downgrade-able 3DS to 9.2.0-20U.
6. Congratulations, both of your 3DS's CPU's are now fully exploitable, and therefore, A9LH and CFW, which require both CPU's to be exploited, can be installed with caution.
All the required additional and extra information can be found here, in this handy guide:
https://github.com/Plailect/Guide/wiki/Hardmod-Downgrade
I apologize for the "Hard Mod Inconvenience", but you're always able to swap your 3DS with a friend who is okay with it (some of my friends have 3DS's they haven't used since 2011, but I personally have no need for them.)
As a last resort, you can also sell your 3DS (buy first if you want to System Transfer), and then you can buy one for a desired price from many different websites and people...
I hope this post clears up confusion, especially for people who are new here.
Andrew21
Yes, you can *barely* launch Homebrew on 11.0.0-33, but not everything will function as intended, including but not limited to; DOWNGRADING
Here's an explanation of why your 3DS isn't downgrade-able:
The 3DS consists of 2 CPU's;
The ARM9 CPU, which deals with Security, Encryption, Validation, etc.
The ARM11 CPU, which deals with Executing and Running Games.
The 11.0.0-33U firmware has patched all of the ARM9 exploits available at the moment, and patched most ARM11 exploits.
A limited amount of ARM11 exploits (Homebrew Launching) still work *mostly* in 11.0.0-33U firmware, including Freakyhax and SmashBrosHax.
In order to gain the ability to exploit the ARM9 CPU, the following would have to be done:
1. Hard Mod your 3DS, so its NAND can be Read/Written by a computer (preferably Windows). Many trusted people worldwide, on GBATemp, offer NAND Mod services (sometimes paired up with downgrading):
https://gbatemp.net/threads/list-of-hardmod-installers-by-region.414224/
2. Read the NAND, and modify its 11.0.0-33U firmware in order to downgrade it:
https://github.com/Plailect/Guide/wiki/Hardmod-Downgrade
3. Write the downgraded NAND copy to your 3DS's NAND, and your 3DS is now partially downgraded, but enough to be able to go ahead with the next step.
4. Due to the fact that the 3DS's NATIVE_FIRM is downgraded, you are now able to fully exploit the ARM11 CPU, which means that you can downgrade even more (which is necessary).
5. Due to the fact that the ARM9 CPU exploits were patched after 9.2.0-20U, you must downgrade your now downgrade-able 3DS to 9.2.0-20U.
6. Congratulations, both of your 3DS's CPU's are now fully exploitable, and therefore, A9LH and CFW, which require both CPU's to be exploited, can be installed with caution.
All the required additional and extra information can be found here, in this handy guide:
https://github.com/Plailect/Guide/wiki/Hardmod-Downgrade
I apologize for the "Hard Mod Inconvenience", but you're always able to swap your 3DS with a friend who is okay with it (some of my friends have 3DS's they haven't used since 2011, but I personally have no need for them.)
As a last resort, you can also sell your 3DS (buy first if you want to System Transfer), and then you can buy one for a desired price from many different websites and people...
I hope this post clears up confusion, especially for people who are new here.
Andrew21
Or others 
. Saves on time, soap, water and money having to wash them.