Can this cause Clutch Slip on 2011 cbr600rr
 

I just removed my clutch plates and found that most of the friction plates were worn in. I also discovered that the previous owner didn't put on the wave washer or the flush washer back onto the idle gear. Can both of these things
https://cimg5.ibsrv.net/gimg/cbrforu...994aeab3cb.jpg
cause clutch slippage?

Yes matey