The real problem here is the leadership deficit. The manager got pushback on the estimates, and instead of explaining the reasoning and bargaining on scope, he caved and kicked the can down the road by letting the estimates crumble. Yes, estimating is hard, and you are probably going to be wrong, but once you have your finger on the scale to get a desired result, you can't blame that on the difficulty of estimating. Just deplorable leadership.
At my current employer, managers love to use this term. We are asked not to gold plate.
And yet they’re the least qualified to decide what is gold plating.
Case in point, gold plating in my managers’ minds means: “code reviewing, refactoring, automating code quality (linting in pipeline etc), or writing any kind of test”. To the rest of us, this is far from gold plating, nice to have, or optional. Yet this is what gets cut every single time. And then we’re asked why we suck so much and “just fixing that one little button” takes a month and breaks five other things.
Refactoring is a bit different in my mind. I often discover better ways to write a piece of functionality while I am writing it. Sometimes it's worth essentially starting over, and sometimes it's not. That decision IMO should be heavily influenced by business deadlines. There are times to push back the deadline because of a major refactor, but they damn well better be a rare exception, and you (and your manager) damn well better be able to explain the business reasoning behind it.
Lumping poorly judged refractors, last minute pet features, and optimizations (actual gold plating) in with critical technical practices like testing and review is probably part of the problem in your organization..
The pipeline stuff is gold plating because it takes longer than two minutes to configure and it then blocks merges and PRs when the code doesn’t pass linting etc (which slows us down right now, never mind that it’ll save a lot of time down the line)
I’m mostly just venting with like minded peers though. At that point, I’ve given up on fixing anything. I’ve tried, it burnt me out, and had no effect. Now I just put my 8h in, get my paycheck, and watch as we’re setting piles of money on fire. You can lead a horse to water etc.
The truth is, your manager's goals are probably more aligned with yours than either of your realize. Part of growing in your career is learning how to make the connection for other people between these unintuitive things that make development faster and the goals they are trying to achieve. I wouldn't give up on finding new ways to share that understanding. It's called working on your leadership skills.
I'll caveat that there are some cases where it doesn't make sense to do the things you described. Maybe you're working on a prototype, or maybe the cash situation of the business is truly precarious. But if you want people to buy in on change, you need to understand their goals and relate to them on that level. Good luck!