I do, not because it's particularly strong, but because the amount of hyperbole applied has gotten so insanely ridiculous. Time after time people seem far, far more interested in venting how worthless their miles are than actually getting any value out of them. Even the awards that are actually easy to get are routinely stated to be impossible to find. You get people routinely spouting out preposterous hyperbolic statements like "never, 100%, 99% etc." that are extremely difficult to make true, and then defending those statements as if they are actually true!

Yes, for most cases the miles are probably not as useful to have as UA, AA, etc, but they're much more usable than people tend to give them credit for. I don't see how spouting out obvious falsehoods and advocating for them as gospel truth benefits anyone.

Time and again I see people complain that there is no availability to XXX, spend 5-10 minutes looking, and find that there is, in fact, availability. The dire claims surrounding DL Skymiles simply do not pass the sniff test. Tougher to use than the competition, absolutely. As bad as complained? No, not even close and it just kills me to see how needlessly pessimistic people get about their ability to use the miles they have.

I have a couple of comments to that. First of all, the question is posed incorrectly - what matters is if I pick a date if there are the desired number of seats available, not who has the most seats on a given route. If for the next 100 days dl had availability on 98 and UA on 99, that doesn't make that route a "win" for UA in any meaningful way - at best UA is better a couple of percent of the time, equivalent 97% of the time, and worse 1% of the time. If I'm interested in the 97% overlap I don't care who "wins" - I'm not keeping a scorecard, I'm using my miles. Obviously these numbers are inflated, but DL's availability at low is a heck of a lot higher than the 1% it'd take to be worse than UA 99% of the time.

Second of all, there is less than 99% overlap between routemaps. Put another way, for >1% of city pairs, there is no option with UA but there is with DL. Even your contrived test fails, and fails in multiple obvious ways. In the past 6 months I've redeemed for a rather mundane but meaningful award to get my sister home for christmas that UA could not have matched, as well as a more aspirational award to La Reunion with a stopover in Paris that UA also could not have matched, because neither they nor their partners fly to either destination.

If you're claiming 99%, you have a lot of work to do to back that sort of outlandish claim up.