Some of the things you mention are not necessarily ebay 'glitches' customers not leaving feedback' 'messages not being sent' are probably not ebay glitches - a message saying your order has been dispatched does not warrant a reply nor are customers obliged to leave feedback - although you could send a message saying ' i can see that tracking shows your order was delivered on xyz - please can you confirm you have received it and that it arrived in good condition, please can you let us know either via messaging or ebay feedback - or some similar message - you will get responses one way or another - although you may not like some of them !
All large organisations seem to work on a trial and error basis with changes - ebay do run trials with selected sellers first but you will never eliminate bugs or clunkiness until it has been run out to the masses and the feedback filters back - eventually the usability is ironed out - in the meantime - scream if you must but patience is the only answer - and feedback to ebay