My two 28/2.8 Nikons live on my cameras. Please don't ask why I own two, it's a long story and not interesting, in fact rather boring, so I will spare you all the retelling and let us just move on. Also one 24 and a 20, Nikons. As well I have a Zeiss Biogon 21/2.8 acquired ages ago for my Contax G1, a beaut lens, taken out once a year to be dusted off.
So the conclusion of the above has to be, I'm not really a 20/21 type of photographer. 28 is my way of seeing the world. Less two cataracts I had removed in 2021 and 2022. So as good vision, 28 or whatever, as I will ever get in this life...
In a nutshell, I use 28s extensively, in fact 95% of the time. My 24 is for 'tight' situations, like church or mosque or temple interiors. The 20 now and then, more to say I've used it than for any other reason. Yes, it does distort, but minimally if handled with care. Otherwise for all my wide angle images, the 24 suffices and the 28s do just about everything I want.
That's me. I own two 50/1.4s I've hardly ever used, and a 60/2.8 macro I love, but seldom take out of its soft case. Ditto a 180/2.8, used two-three times in ten years. Also a 300/4.5, used once when I bought it. My 85/1.8, that's another story, it's my second fave lens, even if I don't use it as much as I should. It's there if I need it or want it.
It's all really a matter of choice. My choices will differ from yours, as they should. As a few others here have said, if you want one and you can afford it, then life is short, toys are fun to play with, so why not?
One comment that may interest you. In my stock photo days, everything I sold to publishers was taken either with a 28/2.8 or a 60/2.8 Nikon. In my film days, a 55/2.5 Micro Nikkor and a 1970 28/3.5. My buyers didn't care about which lens or camera or film or SD card I used to make the images. They wanted the visuals, and I provided them.
As I've found in the course of my life, in almost all things photographic, it's best to KISS.
All this said, if you decide to go for a 21, buy it and enjoy. That's what it's about.