I would like to build a browser based persistent online strategy game. Something in the vein of Evony, nothing requiring a particularly complex UI. I'm a reasonably skilled backend software engineer and hate fiddling around with html/css to try and make UI elements look/behave right instead of working on game design / logic. I've messed around with Unity as well, but 90% of my time still ends up mucking about with the UI.
Assuming I have a webserver with all the communication endpoints it needs already built, are there any good simple 2d oriented game engines for building out a browser-run game? If there isn't really an “engine" with game loops and all, is there a good website design tool that people have used for making games that is mostly drag/drop with UI/JS interactions and exports all the html/js/css files needed?