Hey, I paid over 3 pounds for this app. Are you saying that's not enough to hire an infinite number of developers?! :-)
I accept the point that you can't customise everything, but some of the design decisions seem a little strange to me. For example, I can change the colour of the line between the date and the messages (which, for me, isn't especially useful), but I can't change the colour of the Preview text so that it's different for Read and Unread messages (which I would find very useful). Or I have a choice of Light and Dark themes, but then I'm limited to only using part of the colour palette because I can't choose the text colour for the account name.
I'm not trying to be critical - I've moved to Aqua Mail after many years using K-9, as it was the best replacement that I could find. Just found a few things that (for me, at least) would make it even better.