I run an NC18 on a web space from All-Inkl.com, so I have no roo access, but a little what can I do about SSH.
What surprises me a bit and I would like to know whether this is “normal” or whether I can improve it is the long loading times or the amount of files that NC outputs.
The change from calendar to files takes over 5 seconds. And when I save the page I have an .html file with almost 1.5 MB and a folder full with 40 .css and .js files and a size of 4 MB.
all-inkl.com has servers with php opcache which speeds up loading times - if you haven’t already you should ask the support to move your account to a server with opcache enabled.
websites are nowadays often a hugh mess of JavaScript frameworks glued together, Nextcloud is no exception. you can’t do much about it unless you dive into the development and try to solve things in a different way. Afaik all “modern colaboration solutions” are more or less built this way.