Two settings had a dramatic impact on my FPS. I also use a 3080 RTX.
The first one:
Options → Graphics → Glass Cockpit Refresh Rate - Setting this to low had a huge impact on my performance.
The second one:
Options → Camera → Chase Camera → Instrument Heads-Up Display - Setting this to off gave me more than 10 FPS. I noticed that if you pop into third person with this on, the meters take a significant toll, even when you are back in the cockpit as they stay loaded.
These settings have single handedly made the sim enjoyable/playable for me. Large airlines are still a bit slow – 40-50 FPS, but its higher than 9 for sure.