Sounds like you don't have a good process for handling scope changes. I should know, the place I'm at now it's lacklustre and it makes the job a lot harder.
Usually management backs off if they have a good understanding of the impact a change will make. I can only give a good estimate of impact if I have a solid grip on the current scope of work and deadlines. I've found management to be super reasonable when they actually understand the cost of a feature change.
When there's clear communication and management decides a change is important to the product then great, we have a clear timeline of scope drift and we can review if our team's ever pulled up on delays.
Usually management backs off if they have a good understanding of the impact a change will make. I can only give a good estimate of impact if I have a solid grip on the current scope of work and deadlines. I've found management to be super reasonable when they actually understand the cost of a feature change.
When there's clear communication and management decides a change is important to the product then great, we have a clear timeline of scope drift and we can review if our team's ever pulled up on delays.