This is not unlike the problem that Boeing has with the 737. They've been building on the same platform for decades, riding the FAA policy where you bypass lots of shit if the plane is roughly the same as before.
Eventually, this sort of thing catches up with every design. In Boeing's case, a lot of people died. In Intel's case? Intel will make more money because, to be secure, we need to upgrade all our CPUs
Here's the thing with Intel.
The current microarchitecture in your Intel processor is a layer cake. They've been adding new layers for decades, trying to work around previous layers, trying to squeeze in more speed. They've had to get more and more clever to beat moore's law and basic thermodynamics. And more and more clever to patch around the cleverness from decades past that's impeding them now.
It's a fucking mess and there is no fixing it. At some point, it will have to be rebuilt.
Ars has a good description of Architecture vs Microarchitecture in the "Recap" section of this article. https://arstechnica.com/gadgets/2019/05/new-speculative-execution-bug-leaks-data-from-intel-chips-internal-buffers/
Since it wasn't originally clear to me, I'll pass this on. The word "microarchitectural" is code for "the implementation of an architecture/design". When someone says that the fault is in the microarchitecture, it means that the design was fine. They just implemented it badly.
This is important when reading documents about Intel's speculative execution issues.
I feel like this was the plot of a Helen Hunt movie https://www.washingtonpost.com/weather/2019/05/14/how-do-tornadoes-form-this-drone-based-project-seeks-unravel-secrets-spinning-storms