Should I get the DLCs if I don't plan to play as the rulers they come with?

[Angry Soviet]

To clarify:

I have already bought The Old Gods DLC. My question is, is it worth it to buy stuff like Rajas of India, Sword of Islam, and Sons of Abraham, if I don't plan to play as an Indian, Muslim, or Jewish ruler? That is, do the DLCs add anything to the game besides new factions?

I might get them in the future, but I heard they can be pretty complicated (especially Muslims with the decadence mechanic), so I want to try and get comfortable with the European lords first.

[Jormundgand]

Legacy of Rome is prolly the only one you're missing -- it allows you to have a retinue of elite soldiers to function as a standing army. Sons of Abraham enhances the Catholic experience beyond adding Jews as playable characters -- it allows you to borrow money from jews and the pope (I believe) as well as add the mechanics for electing new popes. If you want to play cathlolic, it's prolly worth a look.

The rest can be skipped if you never plan to play the parts they unlock.

[TentacleMayor]

ROI and SOI would probably be worthless to you. Note that you need ROI for all the India-related achievements, which is stupid. SoA overvamps the major religions in general so you should consider it. btw, Muslim isn't necessarily much more complicated than Catholic, let alone Orthodox. There's no pope, you have one possible succession law, and it's not hard to get vassals to like you thanks to stuff like Hajj and large piety bonuses.Managing your dynasty is the tricky part.

[Evil Crusader]

You need DLCs for, like, half the achievements in there.
Aside from that, Sons of Abraham adds catholic flavor and lets you borrow money from the Pope and from the Jews - which is a pretty useful thing indeed. I'd still lean on getting that, pehaps waiting for a sale.

[Exothermically Eclectic]

SoA: Added stuff for all Abrahamic faiths. Useful for any of them. Holy Orders were added for all religions, but I forget if you actually need the DLC or it came with the patch.
SoI: Can't think of anything it adds if you're not actually playing a Muslim.
RoI: Mostly for Indians, but there are the "convert to culture/religion of your capital province" decisions, which you may find useful.
The Republic: Can't think of anything you need if you're not playing a Republic.
LoR: Retinues, very useful for everyone.
SI: Purely a matter of taste. Some love it, some hate it, some don't care.