That's too bad, if you don't want to play there's a demonstration mode of sorts you can get to by adding only AI players, so you can just watch them fill the map with stuff and then nuke each other at the end.
I'm glad you liked the art style, I'm a big brainlet with art so this means a lot.
The hang up is normal (though 15 seconds is quite long, on my 2700x it's more like 5 seconds) and adding a progress bar would slow down that part of the loading considerably. Might add a message that pops up as soon as you hit Start to let players know this is normal.