What OP described does not sound like a post-mortem examination. Organs and tissue are removed methodically, sometimes it may take brute force to get to certain parts but unless the body was already in a state of serious decomposition then it's a pretty clean procedure as the blood isn't flowing and you can optimise containment of things like faeces and urine. Organs are held together after weighing, inspection and removal of specimens and sure they don't go back like a puzzle but it looks presentable once stitched up. Mortuary technicians are incredibly skilled, if they were messy or blasé about any element of their work it would comprimise what the pathologist could do with the evidence.
Possibly OP saw an anatomy demonstration where the body is fully dissected to explore all the structures for educational purposes rather than determining a cause of death? The demonstrator may go through cause of death, pointing out the pathology but the point of the process is to learn anatomy. Taking a body down to the bones would be overkill for a suspected OD, they could blood test for that and the body wouldn't be examined beyond that unless it was suspicious. But for an anatomy demonstration of course it's not. The deceased and their family would have consented.
Go to the Hunterian for examples of extreme dissection without witnessing the process, they have plasticised specimens where everything was cut away from the nerves, seriously impressive work. I am assuming OP is a student and should have been advised about the nature of the demonstration by their tutor beforehand and possibly debriefed if they are struggling to process what they saw as anything beyond disgusting. I would advise OP to talk to the anatomist/technician if possible, ask them why so much was done to the body that you deem inappropriate.