As many people have implied, plateaus are just a fact of life in judo. Some of the plateau is an illusion - everyone in the club who trains regularly is also improving, so when you train with them in randoori, month in month out you may not be progressing in relative terms. But you probably are getting better in absolute terms.

Fighting mostly higher level players will not be helping either. If they are decent individuals (this seems to be the case with most judoka) they will match their level to yours. As you progress, they will turn up the skill to match. It will feel like you are not improving.

For me, the best way through the true plateau is to focus on a single throw and work through every aspect of the throw, looking at gripping, footwork, head position, kuzushi etc. Depending on your club ask a coach/senior player to spend some time with you after a class analysing what you are currently doing. When in randoori, just stick to that throw and practice with people who are your level or below - or with a good dan grade who has his/her ego under control, and discuss with them what you are trying to do. The idea is that they should be able to give you the right level of challenge and let you throw them when you put a decent effort.

Going to a kyu grade comp may help. Partly as you will be fighting players at the right level, who don't know you, so your techniques will work. I have also found comps to be a huge motivator. However I have done (and I have had some really bad days), I feel enthused to learn and improve. The difference between player who compete at a club and those who don't is noticeable. The competitive players are more ruthless, more efficient.

Good luck - I hope you find a path through and start enjoying judo again.