Pages keeps crashing

Press and hold the shift key the first time you launch Pages after it has crashed. This prevents it from referencing its last application state, and if nothing else is wrong, it should work.

If you have removed fonts that Pages requires, it will crash. If you installed any so-called cleaner application and it thought that part of the internal Pages application bundle should be cleaned, then you may have removed a vital part of Pages and that would certainly crash it.

You may be using the wrong version of Pages for the operating system version and that could crash it. If you profile is accurate, then you need Pages v7.3 thru v8.1 on High Sierra.

You could also boot your Mac into Safe Boot mode, let it do some housekeeping including rebuilding the font database, and then reboot normally to see if that got rid of something that was irritating Pages.