Insulin quandry

Hi since having the Dexcom G6 I have noticed how long my NovoRapid is taking to work on my meals eaten. I have checked sites for lumps (i still rotate areas for injection). I have also checked that the insulin is still in date. I have spoken to diabetes nurse to seek advice and was informed that I may need my ratio changing as I carb count. I advised her that this was not the issue as the insulin works but sometimes it takes 2 to 3 hours to bring levels back to what they should be. I have been on the same insulin for years as I was diagnosed type 1 diabetic in 1968. I wonder if any other members have had this issue after using the same insulin for a long time. I am going to see nurse face to face at the end of May to see if I need another insulin that can act quicker. I have tried to keep my Diabetes under control however struggled as you weren't given the same treatment as now and sometimes I think this has had an adverse effect on my control and life in general. I would appreciate anyone's advice if the same has happened to them.