Great post, @simon.stjohn; sadly, it's become obvious that SP has not improved performance, especially with the extremely poor mobile INP results resulting in a Core Web Vitals failing. I've optimised everything I can and still our traffic has been smashed to the point where I don't believe we can stay on this platform.
Everyone, including SP, has known about the March 2024 Core update for almost 12 months, so it's extremely disappointing that they have failed to improve performance or even bother to offer any advice to users. The lack of communication and zero transparency from SP are also very frustrating. It would be great to actually hear if they have any solutions or improvements under testing or in development. Else, people will be forced to leave the platform.