I doubt any airlines wanted a 50-year old design. But they knew the price & timeframe of a new narrowbody airplane replacement precluded any options except for the updated 320/737. Airlines wanted the added airplanes now, not 7 years from now, although they can be accountable for a lack of long term planning by not advising manufacturers with sufficient lead time for a new airplane to be certified & ready to replace existing fleets. I understand it’s complicated projecting your needs several years in advance, but after nearly a century of commercial air travel, you’d think the art would be more finely honed by now.