The 5800X3D isn't even 2,5 years old, of course an upgrade isn't worth its money. To put it into perspective: If you considered upgrading from a RTX3070 to a RTX4070, the RTX4070 wouldn't even have been released. (Time span between them was longer than 2.5 years.)
DDR4 to DDR5 is a pretty big jump, though. Up to 20-30% on Intel depending on what you're doing.
Of course it might not be that significant on AMD which (IIRC) struggles with higher frequencies anyway and at least for gaming memory speed doesn't matter as much cause of the extra cache.
Whether an upgrade is worth it depends on your workload and how much you depend on it. All I can say is that if Zen5 would have brought the same improvement over Zen4 as Zen4 did over Zen3, I would definitely have considered upgrading. But it seems it's nowhere near it. So yes, maybe AMD just made the mistake of performing too well in the past, and it probably was just a matter of time until they hit a wall. The problem really is how AMD has marketed Zen5, with numbers that simply couldn't be reproduced by reviewers, so it really leaves a bad taste.
