Okay I'm not sure how long you gave it, but it's okay to not like something and also to not have to dunk on any semblance of a failure narrative.
I personally don't enjoy extraction shooters in general, Marathon bucks the trend however, it's clean, tight, engaging and I want to jump in even if I have a tough run. As someone who disengages with most games of this type (roguelikes in general I don't vibe with), new Marathon has something special. It's Bungie at its classic best.
The game does have a S'pht Compiler as a final boss in the final level, I'm not sure I'll ever see it because it's so difficult to achieve but that's okay, I've enjoyed plenty of games that I won't ever see the top tier content (WoW as a prime example).
I can confirm you only need to physically disconnect the non-windows target drive during installation, and as long as you offline the remaining drives after connecting them, windows and other drives will be fine with updates (THIS is the most important part, do it in Disk Management on first boot into windows).
I've run two Windows instances for years, through multiple OS major updates and never had problems with this setup, before doing the offline drive change to each of them, they would both fuck over each other (I had one for work and one for personal).
One thing I did that may be necessary, is I didn't let a boot loader handle the dual boot, I only used BIOS to manage changing the boot target when switching over - I was doing dual windows boots at the time so this may actually be fine with grub, so ymmv on that front.