I should elaborate on the word "proper" in this context.
Intel rarely had the best technology, but it was often "good enough, cheap enough, and available enough" to succeed in the marketplace - this is a lesson SO MANY people forget. Sun, DEC, etc arguably had better hardware, but it was expensive. What Intel was very good at was iterating on the technology it had and making it faster within a reasonable budget. Microsoft is another good example of where "good enough, cheap enough, and available enough" is what usually matters in the market.
Where they started to stumble is when they got greedy. The whole RAMBUS debacle back in the day is a good example of where they took more expensive and worse RAM and tried to make it mandatory. Then there was the whole Itanium debacle, where politics succeeded over engineering and they ended up with a worse, more expensive product that failed in the market. AMD, which had recently acquired a lot of talent from DEC's alpha chip design, then went on and made 64-bit extensions to x86 that Intel had to play catch up to.
Intel (for the most part) ignored the performance per watt aspect of CPU design, which mattered in embedded, mobile, and dense datacentre environments. The result is that ARM came from the bottom up and is now eating Intel's lunch from all angles.
Intel's fabs couldn't compete with TSMC and to a lesser extent Samsung, both of whom could focus on the intense CAPEX (which due to cultural reasons people in Asian countries are willing to take longer term outlooks). CAPEX looks bad on an american GAAP spreadsheet. TSMC literally could take upfront money from apple to build new state of the art fabs and guarantee them a certain number of chips (and keep the money if the iphone had failed in the market). Intel couldn't do that.
Intel spent most of the 2000s era doing $130B in stock buybacks and even if it was run by engineers, they lost sight of the market. Stock buybacks and dividends are fine if you have surplus cash, but chip design is a high CAPEX business.