Rolled the credits and enjoyed my playthrough. I think I'd give it a strong 7/10, but those who enjoy the cinematic side of games more would probably rate it higher - I feel that's its strength.
I didn't often find myself engaging with the stealth systems, as it felt straightforward (and quicker) to just go in fists/guns first most of the time. I didn't really use all the melee/shootout mechanics either, just didn't feel a need to. Combat is generally quite forgiving too - like even if you commit to a punch you can still cancel it into a dodge/parry immediately for example, and there's little to no sway/recoil to weapons etc.
The walkabout puzzle-like parts were the least enjoyable for me, but they kept me playing and those parts got better towards the end.
I did a few of the Tactical Sim missions, got to one where you would fail if you entered 'license to kill' mode which was actually quite refreshing - wouldn't have minded a little of that in the campaign tbh. Although, I think what holds the game back a bit for me is getting into combat not feeling dangerous enough, the stakes felt low, which reduced how engaging playing stealth could be.
Overall I think what they pulled off with First Light is impressive, and I feel with some refinements it could easily go from a good game to an excellent one.