What is wrong with this search on web page feature that you want to disable it?

In Firefox 52 you might be able to use an extension to assign an other action to this key sequence.

• Keybinder: https://addons.mozilla.org/firefox/addon/keybinder/
• Dorando keyconfig: http://mozilla.dorando.at/readme.html

I don't want a different function for the Ctrl+F key sequence: I want to search on the open page non-incrementally. Is this possible?

I'm not familiar with the terms incremental/non-incremental. Could you describe the difference in how it works versus what you want?

One thing that comes to mind: I know some users would like to be able to find one text string, and then keep those highlighted and find another text string. The built-in Find feature can't do that, but perhaps there's an add-on that can do it.

I'm not sure I understand how you want search to work.

With searching non-incrementally you mean that you only want to find the find match and that Next doesn't go to the next match or do you mean something different?