Well, it depends on what you're looking for in the pack.
I ignored the prebuilds in Glimmerbrook because I always do that with premade houses anyway (for anything other than occasionally getting some design ideas). The variety of BB items is awesome though and I've spent hours with them so far, building with them as the focus and figuring out what other pack items they fit with (conclusion so far: Get Together and the recent free BB items)
Surprisingly, I even spent time in CAS, again mixing and matching the new things with the old. I don't feel like there are fewer items in RoM. But also, I have an unexplainable love for thumbnail sweaters and hoodies so those items were a win. But if the style isn't your thing then I get that it'll not feel exciting.
As for the general gameplay, for me a lot of it comes down to the difference between what you *can* do and what you need to do. Just because you don't have to be in the Realm to progress as a spellcaster doesn't mean you can't choose to learn there until the Sim has all the perks and progress you want them to have. Just because you can buy specific potions doesn't mean you have to, you can make it a point to only brew them once you have the necessary ingredients.
I really love that they've left the options open for affiliation to a certain school of magic. I mean, sure, you can max out all of them, but you can also just have a Sim learn the practical spells and some potions and be done with it. Or you can make them an Alchemist only. You can still shape them into a specific kinda magic user, the game just doesn't restrict you to one choice. And then if you want them to do more, they can, without there being a restriction to only one of the branches. I also love the possibilities that the spells open: Repario, for example, is miles better imo than maxed out handiness: you can use it often (well, unless you overcharge lol) and there's no cooldown like with Insta-Repair. Scruberoo makes cleaning faster.
And like nerdfashion said, there are definitely consequences. The curses, while they may seem relatively simple, can throw a spanner into your plans all too easily. Some of them are more showy but some others definitely affect gameplay. It's worth trying to push a Sim to overcharge or try harder potions so they end up with with a curse and then try to navigate around it (again, just because the spell and potion are there, doesn't mean you have to use it. let them suffer for a while :P)
Agreed on the brooms/wands/familiars being more a collection thing than massive gameplay additions. For some, that's enough though. (the falling of the broom at landing animation is funny too :))
I hope you do find enjoyment in the pack eventually. I've personally been playing for the whole week and still haven't even touched my pre-RoM saves to add magic into those worlds. That's a whole different layer to gameplay (balancing the new with the existing) that I'm looking forward to try.