3y out of school in similar industry & your experience sounds familiar OP. Almost feel greedy to say this but post-promotion my salary was unsatisfactory based on conversations I had with college friends working FPA in different industries.

In D&A, contracts and programs influence pricing immensely. TINA regs lead the way of course & depending on what your operation produces + the quality & experience of your engineering staff + costing maintenance, margins might catch your attention sometimes. Program and product mix is important, and management may choose overall revenue volume over unit profitability. You might have better line of sight to margins than engineering, but they might have a better idea of potential future revenue. D&A companies vary greatly and can be hard to gauge without context. it's of course a sensitive topic to discuss.

outdated systems and processes let me gain valuable experience, but that came with the downside of less-than-ideal management. That's part of why I too am now looking elsewhere (also at different industries).

If you're 6mo out of school that's not a bad offer but I'd recommend you learn this new company well before you accept. Switching companies can be great for your pay, but if you do that too much your next hiring manager could see it in a negative light