I am having the same issue with Writer. Opening a document can take 20+ seconds. Closing a document can take 50+ seconds. Saving changes can take 20-50 seconds. I am writing a book, so this is not going to work in the long run.
I have used LibreOffice in a fully wired PC desktop, Windows7/64 bit operating system for 2 years and I have never encountered this. LibreOffice has been really good. I have NO wi-fi anywhere around me. All equipment is wired and not able to be wi-fi.
I have tried both 7.3 and 7.4 Writer. 7.4 became so unstable I uninstalled and went back to 7.3 - but now it is degrading in a few ways… all revolving around saving changes and opening and closing documents. Big documents are a real issue - and I routinely work with 25+ page documents. It’s like the multiple edits are overwhelming Writer.
I reported this to Bugzilla initially and the software improved for about 2 weeks. I am not sure what that was about.