Internet Speed is only half of what I'm supposed to get on my MacBook Pro M1 MAX

Are you using WiFi or wired ethernet with your MBP?

• If WiFi, what band (2.4GHz or 5GHz)? 2.4 GHz will only go up to 500-600 Mbps tops. How strong is the signal? Also, on WiFi, you may be encountering channel crowding from other routers in range, thereby reduding speed on the channel (for everyone).
• If wired, what dongle (exact make & model)? What is the rating of the cable?

What make/model router are you using?

is you are using Wi-Fi to make the connection, it may not be running at its top-rated speed.

Hold down the Option key while you click on the Wi-FI icon on the menubar, and screenshot, photograph, or transcribe the reported parameters you see:

This graphic kindly provided by MrHoffman

if you have an Ethernet dongle, there is one more step required.

Ethernet MUST be TOPMOST.

System preferences > Network

if Ethernet is not TOPMOST AND working, it is NOT being used for your Internet connection.

use the gear icon under the list of networks, choose 'Set service order' and drag Ethernet TOPMOST.

When thew cable is connected, Ethernet will be Topmost and Working and will be used. If the cable is unplugged, the next working interface will be used instead.

if your transmit rate is 1200, your hardware is fine, and other causes are much more likely.

Poisoning Internet performance:

By far the easiest way to cause poor performance, instability, overheating and crashing is to install ANY third-party speeder-uppers, Cleaners, Optimizers, or Virus scanners. or a VPN that you installed yourself. The main reason is that they are relentless in scanning your files, non-stop, looking for virus-like patterns in Everything. When completed, they do it all again.

The idea that a third party, with no special knowledge of the inner workings of MacOS, can somehow find a simple way to protect your computer — that is not already being done by MacOS itself — suggests that the MacOS developers are somehow "holding out on you". That is absurd.

You should remove any and all (other than Apple built-in) virus scanners, speeder uppers, optimizers, cleaners, App deleters or VPN packages you installed yourself, or anything of that ilk.

Third-party file Sync-ers such as DropBox, BackBlaze, OneDrive, or GoogleDrive can ruin performance, but are not inherently dangerous.

Effective defenses against malware and ot… - Apple Community

Effective defenses against malware and ot… - Apple Community

not so fast.

Private Relay and network speed tests

Private Relay uses a single, secure connection to maintain privacy and performance. This design may impact how throughput is reflected in network speed tests that typically open several simultaneous connections to deliver the highest possible result. While some speed test measurements may appear lower when Private Relay is enabled, your actual browsing experience remains fast and private.

from:

About iCloud Private Relay - Apple Support

it is entirely possible that reported speed test speeds, when using iCloud private relay, will be lower than expected. this may be an aberration -- your speed MAY be just fine.

At your Tx Rate of 1,200 Mbps, things look pretty good to me. It's almost the max you can get on 5GHz.

What puzzles me is your channel. Channel 44 is a 20MHz channel, not 80MHz.

ps. the screenshot is fine, there is no personally identifying information in it. just system info

[Edit ... too bad you took down the image; it may have been helpful to other responders.]

Ethernet speeds generally do not decrease with distance form router or busy airwaves. but it requires you move Ethernet TOPMOST

is Ethernet TOPMOST in the list at

System preferences > Network

???

check your internet speed first, you can refer to any speed test websites like nettest.in