You can still use it. OptiScaler can use it with DX12 backend, however there's a 10-15% performance penalty along with the cost of the upscaler.
But FSR4 sure looks good compared to FSR 2/3 and XeSS
Ah I see, I'm merely a flight sim enjoyer and in the context of Jester complaints I thought that the conversation / complaint was Jester not calling out fuel state.
There's no fuel gauge for the WSO pit, he does periodically ask you about fuel state after a while however and depending on what you answer him he can do flightplan/ WP back to selected airfield for instance.
Alot of incoming performance improvements along with other fixed in the upcoming patch, read below. Hopefully it will help you some!
https://store.heatblur.com/blogs/news/dcs-f-4e-post-release-update-changelog
Sort of ancient CPU by todays standards and as previous user stated the F-4 Radar simulation is probably among the best sofar and likely pushing that quad core way beyond its limits. Have you tried the 15E?
Haven't experienced it myself but have you tried to tick the reduced sim rate in F4 special options?
Perhaps try a full DCS repair If it persists.
What kind of CPU / RAM are you running on?