As a 20-year 1K UA flyer also plagued by so many of these delays due to "late-arriving aircraft", I empathize with the OP; but also agree with others that often the solution is elusive. Airlines continue to cut capacity and have mothballed aircraft. Some keep a few ready spares at hubs, others don't; and if those spares are used, they're depleted, at least until the next flight cycle (i.e., next day).

Yesterday, I hit the trifecta but was able to benefit from it: each of the last three flights LAX to SFO was delayed one to two+ hours (coming from EWR and ORD) due to upstream mechanicals and crew availability. I was confirmed on the last flight. To avoid another 2 am arrival, I was able to standby on one of the earlier delayed flights, was the first to clear that flight and got to SFO two hours before my ticketed flight would've arrived at SFO. Had the earlier flights not been delayed also, the original delayed flight would've been my only option.