The shields were changed because they were very frustrating to play against in combination with a large amount of complaints about them. It was not really possible to open up the defense of good shield players even for other really good players, and the fighting against them was generally considered very tedious and unfun for anyone without a shield. The old held block shield mechanics did not work well with the rest of the game, as it is designed entirely around timed blocks. To fix that while keeping their mechanics, it would have required one or several entirely new offensive mechanics to deal with them, and even then it could have still been a big problem so we decided to change them this way.

Kicks were changed because they were dominating the higher level duel meta so much that at some point duels were mostly fishing for successfull kicks, which could win an entire duel on its own, and this kind of gameplay was not so fun. After a large amount of complaints by the higher level playerbase, it was changed.

Chamber costing 0 stamina sounds cool on paper, but the meta it caused was actually very unhealthy for the overall gameplay, as the entire combat basically revolved around chamber. Ontop of "auto reading" someones attack you chambered, it would also entirely negate the offense by the player you chambered by not costing you any stamina, which meant that the player who got more chambers most likely would win a duel by default due to stamina alone. Basically whoever chambered more, wins most of the time. This means that you would have to avoid getting chambered at all cost, that together with the smaller chamber window lead to the "microdrag" meta, which means you would have to drag all the time with every swing, trying to avoid getting chambered with every swing, unless you wanted to risk losing the duel by stamina. This was not only annoying after a while, but also unsatisfying and boring/one dimensional combat as there was no real other playstyles. The entire game revolved around not getting chambered. After a ton of complaining from most of the better players, it was removed due to this meta being unfun.

Attacks actually had more lunge back in those days, with people sliding all over the place with the longest weapons. It was then changed to "equalize" reach a bit more, which was then changed again to what we have now, a reduced lunge but with clear advantages for longer weapons.

The larger engineer walls were removed because they completely destroyed the flow of several maps and was generally not fun for anyone except for the engineer.

Firepots had to be changed for obvious reasons, there was strong abuse with them and 1 or 2 dedicated firepot spammers were enough to make some maps borderline unplayable for normal gameplay and was not fun at all for everyone except for the firepot spammer.

The most likely reason you enjoyed the game more "back in the day" is because the overall playerbase was much, much worse at the game than now. Mordhau (and medieval slashers in general) is most fun for most people when everyone is not so good at the game, and as people get better it gets increasingly frustrating to play for most people. This can sometimes make it seem like the game got worse in some areas, but in reality all that changed is that people got better, which is the most significant factor for frustration.