Define "obsolete." Square-taper isn't the best for racing use anymore, but you've articulated pretty clearly the advantages it has for any other application where durability and longevity are required, but light weight and stiffness are not. Don't get me wrong - outboard bearing cranks are a genuine performance upgrade, at least in terms of weight (stiffness is of questionable virtue). But for most purposes, square-taper cranks have more versatility, an easier to manipulate chain line, considerably more durable bearings thanks to not being exposed to contamination and greater interchangeability.