I’m not sure what your professional experience is in, but as a counterpoint, I’ve never been in a situation where I hadn’t wished for a system I’m working with to already be in a Bayesian framework. Having said that, I only occasionally am building things from scratch instead of modifying existing systems, so I’m not always lucky enough to be able to work with them.

The pain points around getting a sampler/model pairing working in a reasonable timeframe is definitely a valid complaint. In my experience, inference methods in Bayesian stats are much less forgiving of poorly specified models (or said another way, don’t let you get away with ignoring important structural components of the phenomena of interest). A poorly performing model (in terms of sampler speed/mixing) is often a sign of a problem with the geometry of the parameter space. Frustratingly this can sometimes be a result of conceptually equivalent, but computationally different parameterizations (e.g. centered vs non-centered multi level effects).

The struggles are worth it IMO because it is helpful feedback that helps guide design, and the ease with which I can compute meaningful uncertainty bounds on pretty much any quantity of interest is invaluable.