Sales guys very rarely tie their stomachs in knots with "So I suppose technically I might have talked to five million in new accounts last quarter, but most of them required new features, so I'm not sure I can justifiably claim credit for that one without splitting it with the engineering team." One might start learning from that example. Did you lead development on a new product with $5 million in sales? Then I might describe that as leading development on a new product with $5 million in sales. I wouldn't recommend optimizing SQL queries on a screen no one actually uses, but if that is your day to day activity, you were improving performance of the company's flagship product which launched to over $5 million in sales. If you're optimizing page load speed then presumably you tracked the before and after and, if you don't have great data about how that trickled into the business results, you can at least say "I shaved 5 seconds off our dashboard. Research from Google / Amazon / Microsoft / etc has found that page load speed has the following quantifiable impacts and that the sensitivity is on the order of 100 ms, or roughly one fiftieth of the improvement I delivered."

You can also either a) engineer your transfer to the part of the company which makes money or b) engineer your work duties such that they include things which will help career growth. For example, A/B testing both prints money and gives very relevant, justified metrics which are likely to include things motivational to decisionmakers at current and future employers. If you are an engineer in a company which doesn't A/B test but could, you should make that sale internally, and then nominate yourself as the obvious person to implement it.