Why are so many albums poorly remastered onto cd

A lot of newer remasters are remastered with greater average loudness levels than before. The sound can be much different as a result, better or worse depending on the individual preference and other factors.

Louder means clipping often comes into play sooner which may result in worse sound if the amp/speaker combo is not up to the task.

I find only a small % of remasters I have heard are remastered in a manner where clipped waveforms in the actual recording are an obvious problem that makes the recording hard to listen to,

Until clipping produced by the playback system, specifically the amp/speaker combo, is addressed, it is hard to tell sometimes that the issue is more with the playback than with the recording. This kind of clipping can be subtle and hard to detect even at moderate volume until one hears the same recording played on a system where clipping is not a factor in the sound quality at typical listening volumes. I suspect clipping in various forms is an issue with many digital playback systems using less efficient speakers and/or less powerful amplifiers to an extent that many would be surprised by.

there are so many horror stories of different 'master tapes' that are compressed etc while the real masters remain untouched the ones that were toyed with are what we often listen to

what about the obvious:

the master tape ages and when it is used to create a cd, the result is less than pleasant. this would be true for poorly maintained or old master tapes, maybe acetate-based.