Hi.
I have a Netgear Nighthawk R700 at home and I am pretty happy with it when it comes to performance.
However the firmware is OK an nothing more than that. It has all the features I need ( and a lot of stuff that is basically useless) … but lacks QOL features or anything more than just the essentials.
My question is.
Is it worth flashing to another firmware?
If so which one and why?
[Edit: Also Easy and good looking monitoring is a definite pluss! ]
Well, to find out if it is worth the effort, ask yourself how often do you use the UI of that device?
If it is more of a “project” for you … sure, why not! 
I’m running openWRT on some linksys routers and use those as pure access points. Doesn’t really make sense either. 
Ah I am pretty hands on with my home network so I am on there at least a few times a week.
I am more looking for people that have experience with the different firmwares.
How do you like openwrt ? do you use it often or was it more of a “setup once and then never touch again” ?
It does the thing I want it to do. For me network stuff has to work and get out of my way. So if I have the option to use open software without a degree, I’m all about that. But I’m done tinkering with something all the time to make it work. OpenWRT delivers on that front. But I have no idea if it supports your device / if your device will allow you to use custom firmware.
Last thing I flashed was a 56k modem, the flashing went ok but I ended up with problems.
If it works don’t flash it IMHO
Since you said that I wouldn’t do it. Also since it’s something you use every day I wouldn’t mess with it. Maybe you could get your hands on another router to flash to get back into doing those kind of risky operations without risking actually good hardware that you use every day.
My motto is becoming: if it works, don’t try to fix it.
I have done this a few times, mostly with DD-WRT. I usually would only do it to get more functionality out of it. Mostly though I run regular computers or VMs with OPNSense, PFSense, or RouterOS. Better performance even on old hardware than those home routers and more features than I generally need even for business networking.
I flash openWRT on everything, last device was a wifi access point. It had weird issues, rather than finding out if there’s a newer better firmware I just install openWRT and it has 10x better functionality.
Most stock gui’s are absolutely terrible too compared to openWRT.