[Client] Cannot play the game - Launch button does nothing

This issue has slowly gotten worse, at first it just took a while for the launch button to work, now it straight up does not work at all.

This has been happening since Patch 7.3, at first I would load up the League launch screen (old client) and I would have to click the launch button several times just to get to the actual login screen. Now, it takes forever for the screen to load fully on the launch screen, and I've been sitting here clicking launch and trying to get it to work for over half an hour.

The repair button under ? also doesn't work, at all, it does nothing. Restarting the process or ending task the process does nothing. Starting the client again and telling it to terminate the old one does nothing. Sometimes when I click the button it will make the sound like it's working, and even black out the button, but it just goes back to being orange after a few seconds.

I really don't want to have to resort to a full reinstall because my internet is absolutely dreadful and it would take me almost a day to download the game again. Anyone that has an advice how to fix this, I'd greatly appreciate it. I looked through all the solutions I could find here on the boards and nothing works.