I have a personal legit fully activated version of Windows 11 Pro, which has been registered for the insider program. I am very well aware that my computer is part of the windows insider program since I

personally signed up to participate. Why then does Microsoft feel the need to constantly remind me of this by bringing back the evaluation watermark? Very ugly and extremely annoying. Remove it , or at least provide an easy option to do so!

Agreed, the watermark is so ugly, please provide an option to at least hide it.

THIS and YES.
I paid for the Windows 11 Pro upgrade, it is fully and legally activated, and while I am a happy participant in the Insider program I definitely do not consider this an "Evaluation" license yadda yadda - The watermark on my desktop which appeared following this weeks build needs to GO.

I find this extremely annoying.

I don't want a bunch of white text in front of the desktop image when the taskbar is hidden. I find it extremely annoying when (ⅰ) I'm using the computer at night, and bright high-contrast text appears in the corner (solutions include not hiding the taskbar, which is worse than the text, or putting a dark window over it, which is annoying) or (ⅱ) I'm using my OLED TV as a display and want to minimize burn-in risks. With respect to the latter, I typically have a black background and hide the taskbar, and when e.g. I leave the room for a few minutes, I typically just click the 'Show Desktop' corner shortcut and move the curser to the right edge, which results in the entire screen turning black (which, in the case of an OLED, is indistinguishable from the TV being off, except for the latter activating a standby light). Some workarounds for this include

(a) turning off the TV, which also turns off the receiver—if I want to do something like play music in the background, this isn't an option, and it is also annoying because of the extra steps and delay turning it back on and having to correct the receiver's CEC source selection acting weird sometimes (I use CEC for other things and am not disabling it) and reselect the sound mode on the receiver if I wasn't using default (e.g. all-speaker stereo for music or DTS Neural X instead of Dolby Surround),

(b) opening a black image in an application that has a full-screen preview option—also an annoying extra task to do each time, and requires an unnecessary app to stay open,

(c) use a screensaver—I do, but manually using a shortcut (this is the best workaround, but it requires an extra icon on the task bar, and it isn't as quick since you have to target something instead of just going full bottom-right, unless I want to waste a hotkey slot for it and use the keyboard), since screensaver activation is oddly unreliable on every modern Windows computer I own, plus it doesn't activate immediately so I don't know if it worked or not until I get back—being able to manually achieve an optimal result by just clicking the bottom-right corner and then leave is much nicer, or

(d) rely on a custom power profile, which has similar issues to the screensaver, except that I can't manually engage it with a shortcut (as far as I know), and I really don't want to have another random customization that I need to remember to add on every device or re-add after a reinstall, plus I don't want the screen turning off after a bit of inactivity when I'm actually using the computer (e.g. reading something on-screen)—nothing beats quick manual activation (and restoration is achieved by just clicking in the bottom-right again).

So, the only decent option is what I mention in ⅱ(c), which is still inferior, plus it does nothing for ⅰ. Why do I need a permanent reminder in the bottom-right of the screen that the operating system I went out of my way to install is still installed? I can see someone maybe liking it if they flip through VMs or multiple computers on the same display, but that is still pretty tenuous and niche, and there are very simple ways for the minute to non-existent set of people with that combination of need and preference to make desktops distinguishable or report OS information (an obvious method would just be to create a custom desktop image for each device). In any case, the hypothetical is almost silly, and the number of people who are annoyed for the reasons I listed or others is far greater, and orders of magnitude more people having to set up workarounds (which is more time-consuming per case than making a custom desktop image) instead of a tiny number having to open up paint and modify an image is obviously inefficient.