I was going to make a similar suggestion, so maybe it can fit here instead.
A possible solution to the implementation of filters in the plugin section could be community based filtering.
Users could confirm which plugins work on certain versions, and that data could be used to help filter out what you want. Let me give a quick example on how it could work:
User downloads "emerald example v1.0" on his "spigot-1.13 server"
Confirms it's working, so that plugin could be added to the '1.13 compatible plugins list'
Another user downloads "emerald example v1.0" on his "spigot-1.14 server"
Confirms it's working, so that plugin could also be added to the '1.14 compatible plugins list'
Lots of users have been downloading "ruby example v1.0" on their "spigot-1.14 servers", but have been reporting it as incompatible, so the plugin could get into the '1.14 incompatible plugins list'
After a while, an update comes out for "ruby example" now 'v1.1'. This new version would be able to get into the '1.14 compatible plugins list'.
Some UI changes would be required on the plugins main page (for the filtering of "Downloaded Plugins" and "Compatible Versions"), to each plugin's page (the addition of version badges, matching to the user's server version for each released version and a "thumbs up/down" for the filtering).
I'm sure I didn't think of everything that would be possible, but maybe it'll give some ideas on how to possibly work on the filtering system.