I had the same problem when I bought my R1300GS in December 2023, went from a less than 12 month old R1250GSA Trophy with all the options and multiple insurers wouldn’t even quote me even though on paper the invoice price of both bikes was more or less the same.
This year renewal time it went UP from about £600 to over £900 with Bemoto. I queried it and they said it was due to the bike being over £19,000 but I reminded them that the value of my previous was £21,500 and this didn’t happen and didn’t have an answer.
But even factoring in the current value of my bike being closer to £16,000 (BMW offered me £13500 to trade it in against the new GSA) the quote was still in the high £700’s and several insurers flat out refused to insure me.
47, riding for 20 years, garaged, tracker, physical security, medium risk area in NW England and full no claims.