That is a giant nothingburger with a lot of words.
This is pretty much true for all bow users. You could write the same about Childe, you also don't take along Fishl for her damage but for Oz.
You can't use every character in every setting the same way. Yoimiya works great against boss opponents and if you use her right, she can easily be the main dps.
I rolled for her, because I got the Skywind Harp through the standard banner and of all characters I can have atm and for the near future she is the only one who benefits the most of that weapon.
If you don't need or want her, that is great. But to be honest there is a lot of copium getting thrown around because people want to skip her for Baal. This is ok and if she is not that great, it is getting easier.
Now I get that it was a huge post and not everybody will be motivated to read it, but if that's what you got out of it, you clearly missed something. Some of the problems of bow users as a whole are brought up in those gifs, but I just posted them separately because they were funny.
The big problems with her specifically are more related to pitiful multipliers on the first half of her normal attack chain when she never gets to use the last half of the chain since she has to dodge. Her burst of all things only targets one enemy and it's actually able to and frequently does miss. No hitstun, no AoE, the artifact set built for her is one of the worst for her, her kit has no rhythm, Her charge attack homing arrows don't work if the enemy is at range (this one makes no sense and hopefully is just broken and not designed that way). There's even a whole part showing why Xiangling is a better and more consistent Pyro main DPS. There are videos showing that against a single "large" enemy, she's still not as good as a 4* support in the main damage role. For a limited 5* character. That's a pretty bad precedent.
Childe has none of her problems because if you're using him to auto fire normal bow attacks you're playing him completely wrong. Main dps Fischl players are probably in a similar boat but even she doesn't have the problems with her Elemental Burst missing enemies and only hitting one of them even if it connects. Also, Oz cannot miss as a skill where as Yoimiya's skill can totally be wasted.
Anyway, in my opinion she needs a lot of work. I thought so before the reddit post, but it does a great job of pointing out some of the more glaring issues with her. I'm happy for you that you like using her, but I don't understand why you wouldn't want her kit to improve when it badly needs it.