I'd rather every element be a div than do one minute of editing those stupid jinja files.
20MB of inscrutable JavaScript allows you to have a) a sane structured component system where you can actually build up UIs compositionally rather than a flat glorified string substituter (i.e. not actually "just template rendering"), and b) the control and abstractions needed to make good UIs out of nested tables.
Sure, but you're still going to be using "20 MB of inscrutable JavaScript". (Unless you use Wicket, but I'm not sure that's an option for emails, and would likely trigger the same complaints anyway). I mean, I hope you're not using the component style rendering layer for Python that I published ~10 years ago, because I haven't maintained it, and as far as I know there aren't any others.
As a home assistant user, jinja in yaml files is hot steaming ass.
Every time I read the jinja manual I want to cry. And a small part of me dies in side. It's like a templating language designed to get even with the person who microwave a tuna fish sandwich in the office, for lunch, daily... That some how leaked out to the web.
While generating any moderately complex HTML on the front end is a pain in the ass for me. I prefer avoiding it. If I need to request some data from the server to dynamically update the page with, I just make that endpoint return some server-side-rendered HTML that I insert wherever it needs to go.