No one's ripping you off, it's an easy industry to moan about, nothing new there. If you really think that's the case you could look at your insurers Net Combined Ratio (NCR), if you can't find it for your provider, the industry as a whole publishes it each year. That's the comparison between settlements and costs compared to premiums. A couple of bumper years in the pandemic, followed by a loss last year, the ratio is never less than 9/10 usually 9.5+. Those are the margins, that's the expected shared risk, your insurer is hoping to make 5% profit from combined premiums. That's not to say everyone is paying the right premium, just that it balances out.
Always worth shopping around or negotiating, but I'd be surprised if an independent broker could offer you something better than you could find for yourself. For non specialist policies they can't usually compete, their commission is greater than the insurers margin, that's why so many have disappeared. Insurance is hugely profitable due to volume rather than margins, re-visit this in a years time and see the relationship between the premium hikes and profits.
You've already detailed the causes for the increases, so I'm surprised you weren't expecting it. I got an indication of the scale when I tried to hire a car last month. The local branch of the national chain which is my first choice, had nothing available, half the fleet is out on longer term loan.
