How to advocate for myself when my boss doesn't?

How to advocate for myself when my boss doesn't?

Over the last 5 years I've created a role within my department, expanded to take on a direct report, was promoted to report directly to dept head, and have become a touch point for my group when it comes to my work. Last year we went through a reorg and I was assigned a new supervisor who has not worked in the same areas as me, so it feels as if I've spent much of my time training them on how to run my team. I lost my direct report in the reorg and a new hire was reallocated to them rather than me. It feels as if in the past year I've lost a ton of autonomy, and though I am continuously trying to progress it seems that there's a loss of ownership over my role, as mentions of my contributions are now put in favor of "supervisor brought up an idea" that I had put forward. While it might not be strictly true, it feels like I'm putting all of my effort into bolstering my dept's successes to the benefit of middleman lead of the team I used to feel direct ownership over. Any suggestions on how to work with this person more constructively?

It's personally difficult to have been in a position of progress and feel as if I'm backtracking while simultaneously contributing to another's success, but I obviously don't know how to broach the subject of needing more independence from my supervisor with either them or dept head.

I'm guessing the answer is that this is how the team is structured and I have to deal or leave but just wondering if anyone has dealt with anything similar and has any advice. I do love the company but am feeling diminished in my role, whereas before all this was feeling constantly encouraged to reach further.