Having played a21 a while, I'm not a fan of the glass jar change. It does improve the early survival aspect, which is good, but the implementation (removing the jars) causes other problems, at least in my view.
Mostly, it just seems bizarre that we can't carry water from a water source and purify it. That's been basic human behavior since the dawn of time. The analogy with gas cans is flawed in my view, because that's just a system that was itself messy: the correct fix for that would have been (and this would have been a gameplay improvement I think) to require finding or crafting a gas can to carry it around in, and maybe even a siphon or hose to collect it from gasoline sources.
Aside from how it feels to not be able to collect water or to just have jars and bottles wink out of existence as soon as they're emptied, another issue is that this change ties players to the traders and quest system even more. You have to access a trader to get a water filter, now. This won't be a problem for new players, but a lot of us have played this game enough that we change our gameplay in order to keep it a challenge. Steam's claiming I've got over 8,600 hundred hours in (which is probably a Steam bug, those numbers aren't all that reliable, but I'm sure it's not too far off.) I actually prefer to play without using traders at all just to jack up the difficulty (insane, low loot percent, all those already set) but that's not really an option in this build. Making the filters available via dismantling something or by looting would sort that issue out in my view.
The change I would have preferred to have seen would have been to remove the option to craft jars, and set the max stack size to three (or so.) The most expensive resource in the game is cargo space, and water is heavy, so that would limit how much a player carries around or stockpiles.
Alternatively, allow players to carry water in unstacked cooking pots, which could then be boiled to produce drinkable water. This would at least reduce the conceptual issues with not being able to carry it around.