No one is saying blends are a problem. There's just no benefit or point to using them.
Changing every 3,000 miles is a fine recommendation and has merit but it isn't due to dust/pollution.
There's 10's of thousands of UOA samples showing that's not the case. Let the data speak and get a UOA if you're unsure - at 3,000 miles the oil will test way under limits on an average daily driver with no current issues.
Manufacturers have intervals far exceeding 3k - often double or more. Subaru itself says 6,000 miles and most individuals exceed that as well, and Subaru's easily run 200,000 miles all day long many 10's or 100's of thousands of times across the united states.
If an engine has so much silicon/dirt intrusion that the oil needs changed in 3,000 miles then something is terribly wrong and will probably damage the engine if it's continued to be run even with 3k change intervals.
What was said earlier is spot on:
Low oil is far more problematic than any other oil decision, changing often helps keep an eye on leaks/consumption.