At a previous job the management team got all excited about KPIs and made each dept come up ~5 of them and then report on them weekly (or maybe it was monthly). I fought it tooth and nail arguing that it was both silly that we were coming up with them and how easily it would be gamed. My concerns fell of deaf ears and instead we wasted upwards of 4-6 person-weeks of time building tools to extract data from Jira to serve as our KPIs. We wrote the damn code to calculate it, of course we know how to juice the numbers. It was a huge waste of time, nothing interesting came out of it (for us or any department), and "management" patted themselves on the back for "taking action".
I'm not say all metrics suck and are a waste of time but you better have a very good reason for them before you go all-in.
A friend of mine's company started requiring all their developers to track their time, down to the 15min interval. I'd be looking for a new job within a week. Don't even get me started on how asking your employees to track their time is essentially asking them to lie which means the stats you get are worthless, worse than worthless because time tracking takes time on it's own to do.
Coming up with a new idea, researching its feasibility, and executing on it isn't really doable with rigidly monitored metrics, because a lot of the productive work on novel things looks like thinking about things and trying things that don't work out.
As a field we have yet to find good metrics for coding performance, anyone who tells you otherwise just wants to have an excuse to fire you when they suddenly decide that you no longer serve their purposes, even if those purposes is just to have a cool social club that validates their fragile ego.
Are you implying managers don't directly contribute to a product? Because wow, you're really either horribly naive or wildly narcissistic. As a someone who managed programmers for almost 20 years, only a fraction were hands-off. Why do you think all the 10x engineers become managers? A high performing manager hits targets, ships products, and makes customers happy. If you think a hot shot programmer on a team can do this all by themselves, I don't know what to tell you. You'll have to learn the hard way.