How are you actually handling multi-provider EO data fusion (optical + SAR) in production?

Working on something that needs to pull and fuse imagery across providers, and I keep hitting the same wall: every provider has its own auth/API quirks, the formats don't agree with each other (GeoTIFF vs NetCDF vs raw SAR products), and the processing cost climbs fast once you're doing this at any real volume.
For people who've actually shipped something on top of this (not just a research notebook) what did your stack end up looking like? Built everything in-house, leaned on GEE / Sentinel Hub / UP42, or landed somewhere else entirely? And roughly what fraction of your timeline went to plumbing versus the analysis you actually cared about?
Trying to figure out if this is just the cost of doing business here or if I'm missing an obviously better way.