Lanefan
Victoria Rules
There's a million possible reasons, all of them valid, eventually ending with "because I felt like it".You cannot have both of these things.
The GM cannot simultaneously be someone with control that, and also a human merely implementing something they had no control over and thus you can't get mad.
It's either-or. Either you have control, or you don't. If you don't, why is your game so far out of your control that you can't even decide whether something gets included or not? Have you lost control of your game? And if you do have control, then why aren't you responsible for taking things away from your players?
You will never get an analogy between something like "we cannot make a game bigger than one megabyte, so figure out how to make that happen" and "I, the GM, freely elected to remove dungeonrisen from this game". Because the latter is not, in any way, forced.....except by the GM. So it is perfectly reasonable to say, "Uhh, GM, why did you ban this unobjectionable thing???"
I should note that IME decisions like these are made well in advance of any players being invited in, such that on being invited in you can ask "Can I play a dungeonrisen?", I can say, "Sorry, no you can't" and you can add that to whatever other factors you're considering when deciding whether to accept or decline the invitation.
By the time I'm inviting players in, I've already done all the design work: you're being invited in to a fait-accompli rules-set and setting, and you're free to decline said invite if you wish.I mean, sounds to me like a lack of imagination on your GM's part. I'm more than willing--eager!--to put in the time to make something like that work for my players. If I have to draft an entire new class just for their use, I'll bloody well do it.
Having to incorporate something big and new - e.g. a new class or playable species - at the last minute would delay the campaign's start for weeks while I rewrote my game's rules and lore in order to accommodate it, which ain't exactly fair to the other players who are ready for puck drop right now. (in long-range anticipation of a campaign reboot at some point, last year I rewrote my system to add in a new class; perhaps worth noting this is a class that was suggested by a player. That process took over two months - some of which was, admittedly, me arguing with website coding which I'm not very good at - meaning I'd never want to have to do it on a last-minute basis.)

