If you do have experience with these lenses, why act like they don't provide a value?Well sir, I would say the opposite is true for you, you ain't got the RF glass, you ain't got no clue about it! I however, and in point of fact, I have $15,000 worth of RF glass. Now, if I told you I had owned the Tamron 70-200 G2, and that I had owned the Sigma 85 Art, and the Sigma 12-24 Art, and the Tamron 90mm Macro, would you believe me? If it gets more modern than that let me know.
Why act like purchasing products based on how well they suit your needs is sad?
Why pretend the people who purchase third party are unaware of what they are buying?
Why make such strange assumptions about the business practices of third party manufacturers.
It's not just about downgrading the quality. It's just different design priorities that allow different manufacturers to target different customer types. Size, weight, optical quality, price, everybody has different priorities.
Each manufacturer operates in their own niches. Just because Sigma and Tamron typically target a lower price, doesn't mean that the quality they provide relative to this price is anything to sneeze at. Especially the most recent designs that are currently not available in RF but in L and E mount show great performance. And there are plenty of design niches that Canon hasn't ever made any efforts of directly competing in, like they Sigma 18-35 mm 1.8, 60-600mm 6.3 or 14mm 1.8.
If you want to act like a snob and feel sorry for the people who buy 'lesser' gear, go ahead. I hope there's a Leica user out there who in turn is sorry for you.