I've recently tried this and got burnt. Spent a week of my own time doing a (what I believe to be) pretty serious improvement to both code structure and runtime

I've recently tried this and got burnt. Spent a week of my own time doing a (what I believe to be) pretty serious improvement to both code structure and runtime behavior for a very green-field project. Showed it to Product Owner "This looks great to me, but you should talk with X see what he has to say". Talk to X, total subjective dismissal. Now I could go on the offensive and push my vision slowly but certainly, but I won't. Ultimately, I am not responsible for the product, nor for the product owner or colleague's (ignorant?) attitude, and truly I don't want to spend my time improving more than what is *wanted* in the project and my own craft. I would have better spent the time doing Leetcode than trying to improve this and I find it hard to see why I would engage in something 'slow but certain', against odds, for something that doesn't truly benefit narccisistic me.