For me, if it's an application ui/ux, then the rendering should be almost exclusively on the front-end. It's just delivered via a web server instead of installed. Yeah, it's larger than server-sent. It's also emphatically not tying up server resources for template processing, instead using the super computer on your desk or in your pocket.
I frankly feel ill when I see more than a couple hundred kb of compressed JS go over the wire... why a couple hundred, that's just where I draw the line... React + MUI with some optimizations and all the application logic should easily fit in under 300k compressed payload. If you're going over that, you're probably doing something very, very wrong. Not that you can't go much smaller and hand crafted. It's a trade-off.
I also think edge development tools like Cloudflare Workers and Deno are exceedingly nice and can seriously bridge the gap closer to server rendered, but still not the same as a lot of classic legacy apps.
On the flip side, I look at how much memory and resources applications use on a server as it is... They're often massively under-utilized as well. So who knows. I just know that there's nothing wrong in using the client's system to render the client.