The quality of correction is top notch with MA1! Genelec has way more simple EQing in their program and you need the extra unit which is more expensive as MA1. And you can use the MA1 mic as normal measurement microphone with other software, you even can download the correction files for it! (that alone makes the price ok)
When buying these speakers and you can't afford a 100 bucks interface ... sorry that's simply part of the costs for the system. As most users already have microphone inputs in their studio ;-) that's not really an issue.
GLM software is way better connected and has tools for remote control and surround setups. Neumann is lacking there and definitely behind! And they are slow in catching up ... but there is at least some movement. A good remote control is definitely missing!
I did a few setups and trials with KH750+KH80, KH80 and KH120ii and never had a problem with the software. It's limited in functionality, they should give way more options and maybe a control pannel for level/muting/presets etc.
BUT - the quality of the correction is VERY good! Even with a pair of KH80 you get reliable results in not so good rooms. As it not only corrects frequency response but also phase/impulse response (at least they tell so) it's not just some EQ settings as you could do with a MiniDSP. Especially for a HiFi user with not to much KnowHow it would be impossible to dial in a "perfect" correction - and you still need a measurement microphone and interface and need to learn REW. And it's way more expensive. I don't see how this should be simpler?
Volume control with digital connection - I use of course my audio interface as all professional users will do (after all it's not aimed for the HiFi market - they probably should bring a range for that?). But there are fairly cheap devices which can do that job, like this one:
https://www.amazon.de/dp/B0CDX16FWT/
Many use a WiiM with it and there are for sure more expensive and more fancy preamps available.