The lead time on a national magazine ad was usually longer than a month and they generally weren’t tied to a specific magazine’s publishing schedule— they were probably parts of longer thematic/strategic campaigns. They probably also appeared in trade rags for other tech-heavy (mechanical engineering) or tech-adjacent (finance) publications.

The real reason ads look shittier now is the marketing world shifted their investment from the ads themselves to ad targeting. You just don’t need to make great ads if you can shove them in the face of the most receptive people at the right time. It’s also not feasible to make a few great ads when your marketing team has 8 different approaches tailored to specific demographics in multiple languages.