Only frame that makes survival fun for me. I started playing shortly after Koumei was released so she was one of my first frames too.
I know ppl had some thoughts on her, how's shes painted to be a beginner frame and what not, and while i agree that Koumei is not a good frame to give to a new tenno(Again, she was one of my first frames so I can offer up some thoughts) I still had a lot of fun with her and her kit is what pushed me into learning more about the game.
But- not every new Tenno is going to have the foresight and or time to watch and read hours upon hours of content to get a basic understanding of how something as important as status effects work, heck, how even half of her decrees work/ their benefits.
It'd be way to much for a new Tenno to understand.
Instead, I believe that Koumei is good frame for middle stage Tenno. By that point you'll have a basic grasp of how the status effects work and have an idea of what her decrees will offer(assume that they've played a bit of durivi/circut)
The reason why I think she's a good middle stage frame is because her decrees encourage you to change up your playstyle. Rather then just running it down main with your primary, her decrees want you to roll, aim glid, wall latch, and slide. Basically get a better gripe of the games movement system.
Tossing in things like getting kills while sliding shows you that melee has a different attack animation and combo set, or getting kills while airborne might show you that enemies have reduced accuracy while firing at you, rolling offers you slight dmg reduction, encouraging to constantly be on the move rather then sit in a corner, etc etc etc.
Edit- Also want to add that mercy/finisher kills are also a something that can be incorporated into your gameplay and paves the wave to modding your parazon for more then just auto breach. 
Not to mention, she makes just about any weapons great. Dmg buff, ammo efficiency/amount, fire rate/attack speed buffs, additional elemental dmg, etc etc etc.
There's obviously a lot more to expand upon for her but that’s a hefty essay and I’m not feeling it rn lol.
yeah, this was a little bit of Koumei propaganda, shoot me.
