But then, things moved on, standard ways to add more cache with multiple cores was lapped up and later on we found a design flaw that echoed back for a decade or more upon all these multi-core CPU's.
Though in fairness and to put some context upon all this, CPU design is more complex than writing TAX laws. Yet we have exploits for TAX laws appearing and used all the time by large corporations. Whilst the comparison is not ideal and some would say, unfair. It does highlight that nothing is perfect and what we may class as perfect today (or darn close), could and may very well be classed as swiss cheese in the future. It gets down to how far away that future is.
After all, we still have encryption utilised that we have (on paper) shown to be flawed to future quantum CPU's!
But in a World that was aware of Y2k decades before the event, the penchant of business to drive everything to the last minute for profit will always be a factor in advancements. After all, if CPU cores had isolated caches instead of sharing, then that would mitigate so many issues, yet it would cost more to make and most consumers would not appreciate the extra cost for what to them is little value in return above and beyond the cheaper solution. That's business for you and CPU's are made by them for profit.