Lanefan
Victoria Rules
My campaign is based on what D&D looked like about 30-35 years ago, and any future campaign I run likely always will be.Another thought does occur though. You mention the idea of a dwarven druid being a problem in your setting. But, the thing is, in D&D, there are half a dozen druid archetypes that fit dwarves without any problems. Circle of Fire Druid, for example, is a fire worshipping druid - perfect for a forge priest. But, since your campaign was created over a decade ago, everything in the campaign is based on what D&D looked like then and not now.
If I ran a new setting every two years I'd be doing nothing but build settings; the last two settings I've built have taken about (1) a year and (2) about a year-and-a-half of work. With (1) I did some of the work ahead of time and some of it after play began (I wasn't expecting to resume DMing so soon after my previous game ended but got talked into it); with (2) I did almost all the work ahead of time.I think this goes a long way towards explaining differences. To me, a campaign based on D&D as D&D looked ten, twenty or thirty years ago isn't something I'm even remotely interested in playing. There's too much new stuff that I want to try. So, campaigns and campaign settings are disposable to me. If you run a completely new setting every two years, then your setting will much more easily incorporate any new developments that have appeared in the game.
And if that's how you roll then more power to ya!The game adds artificers? No problem. Next campaign will have artificers if someone wants to play one. Players no longer assume a human dominated setting and want to play what would once have been really weird races but are now pretty common in the game? No problems. This next setting will have space for anything you want to play.

Me, I'd rather hew a lot closer to Tolkein if possible. Sure if a new class holds interest I might adopt it (or, more likely, design my own version), but I'm not in the least interested in having what seems like every species in the setting be PC-playable.
I guess my experience with different DMs is that each one has always had their own setting(s) with rare if any overlap. Our settings are often connected in that occasionally characters or even entire parties from one will end up in the other for a while, but the settings themselves remain disparate and under control of just one DM. Whcih means, if a character or party jumps settings that character/party is suddenly playing under a different DM.Of course, all of this is predicated on the idea that campaigns and campaign settings are collaborative efforts. I talked about the dwarf druid having a bespoke spell list. To me, I'd just hand that off to the player with the admonition of choosing stuff that that player thinks looks about right. IME, players will always be far, far more concerned about balance that I will ever be. If something turns out to be a problem, we'll deal with that then. Otherwise? Go for it. Impress me. Show me what you can do.
Works so much better and it's so much easier on me as a DM.
Then again, I come from a gaming tradition where we always rotated DM's. It wasn't until much, much later that I became the only DM for the group. So, the idea of D&D as collaboration has always been part of my experience. That's how I started playing. So game worlds were always a collaborative effort based around consensus. Bob adds something, Dave adds something else. I add a third thing and then Bob changes what Dave added and so on and so forth.
About the only thing we sort-of try to co-ordinate is universal time; such that if, say, character A jumps from my world to someone else's, spends X-amount of time there, and then jumps back, I know how long in my-world time it was gone for.
I've hit that point in the past now and then. Fortunately, right now I'm happy to keep going with my current game/setting as long as anyone's willing to play in it, as it still has more than enough "legs" to keep it going for quite some time.The very top down approach a lot of people advocate for was not how I learned to game. And, when I met that kind of table, I very much found it not to my taste. I'm currently on full time DM duty because no one else is stepping up. The second someone volunteers, I'm out of the DM chair so fast my pants catch on fire.