Does Twitter load without JavaScript? I do not think the tiny number of uber-nerds who disable JavaScript have any effect on Mastadon.
Twitter definitely does not load without loading several megabytes of Javascript. Nitter.net is a quick and easy substitute that loads instantly without it, though some video playback still requires Javascript (HLS video).
Doing so also breaks all web applications (and web applications posing as websites, i.e. React rendering) so it's not something I turn on permanently. I usually only disable JS when my phone is running low and I'm not near a charger, or when I'm trying to read something and the terrible website hijacks scrolls/taps/somehow makes my phone run hot doing stuff in the background.