Yeah, they've had QB issues for most of the past decade, and they'll probably also be without OC Brady fairly soon.
If Aranda leaves they'll probably be fine on defense, they've been solid there through different DCs.
They've had QB issues since JaMarcus Russell left. Mettenberger had a pretty good year in 2013 (3082 yp, 22 td, 8 int), but outside of that, QB play has ranged from "game manager" to flat-out awful until this season. In fact, their offenses, as a whole, have been very average this decade:
2010: 29.7 ppg / 341.3 ypg
2011: 35.7 ppg / 355.1 ypg
2012: 29.8 ppg / 374.2 ypg
2013: 35.8 ppg / 453.3 ypg
2014: 27.6 ppg / 387.5 ypg
2015: 30.3 ppg / 437.3 ypg
2016: 28.3 ppg / 423.2 ypg
2017: 27.2 ppg / 411.1 ypg
2018: 32.4 ppg / 402.1 ypg
2019: 47.8 ypg / 554.5 ypg
These days, 30 ppg / 400 ypg is basically a "Mendosa Line" for most FBS offenses. Outside of 2019, they've basically been hanging right around that line this entire decade. Joe Brady comes on and suddenly, they have an elite offense. He won't be there more than another year, if somebody doesn't make him a HC in 2020. Lose him and Burrow, and I could see their offense reverting back to it's recent historical norm, and them slipping back to 9-4/10-3 land.