In a discussion about how TSR changed some of the base assumptions of Planescape late during the 2e AD&D era (with the removal of the factions as legitimate political powers in Sigil, instead being banned and having to operate outside of sigil or secretly through the now resurgent guilds in Sigil), many people described how they saw major changes to established settings like this (and the changes to the Dark Sun setting for example) as being an issue of “throwing out the baby with the bathwater”.
Personally I think major changes to a setting like this are a boon to players and game masters.
In my opinion, changing a game setting through supplements is a great idea. It allows game masters and players to decide which VERSION of a setting they like best.
Prefer the “changing world” of Dark Sun 2 to the “quest for survival” of Dark Sun 1? No problem. Pick the one you prefer and play it.
Same thing for every setting. This particular change allows GMs who weren’t fond of the existing structures of Sigil to play in a more chaotic, changing Sigil without having to deal with people telling them “that’s not how it works”. And the GMs who love the original factions and setup of Planescape can just ignore this material.
Don’t like the disarray of the Imperium after the assassination of Emperor Strephon by Duke Dulinor? No problem, you can play in a pre-assassination environment instead of following that part of the Traveller timeline.
Fourth Corporate War get in your craw and ruin CyberPunk for you? Ignore it! Or do you want a more military style of game with more open fighting between the corporations? Then run with it.
Multiple versions of a setting are a boon, not a bane. Take a setting and look at it in two or more ways, different ways to play and enjoy your favourite game.
For a good example of this, look at the Star Wars universes. People don’t bemoan the variety of different universes available to play in – instead it becomes a huge selection of different timelines that you get to pick from to play in a setting more to your liking. Don’t want lots of Jedi, and like playing in a setting where the good guys are vastly outnumbered? Rebellion era! Need more Jedi and politics? Rise of the Empire! Even more Jedi, not all on the same side? Knights of the Old Republic! Every change to the setting is not an attack on the other settings, it’s a new choice in game style that you can play or ignore.