The landing marker theory isnt completely dead but it's definitely lost a lot of credibility over the past couple of decades. The main issue is that the lines themselves are way too soft to support any kind of craft, even a light one, and the desert surface would have just churned up the moment anything tried to land on it. Von Däniken's original claims never really held up to proper scrutiny.
That said I do think people throw the baby out with the bath water when they dismiss the astronomical alignment angle. Some of the geoglyphs line up with solstice and equinox positions pretty precisely and that cant just be coincidence given the scale of the construction effort. My money is on a ritual or calendrical function rather than anything aviation related.
What I'd love to know is whether anyone here has looked into the newer LIDAR survey data from 2022 - they found something like 168 previously unknown figures and some of them are quite different in character to the classic animal forms. Genuinely changes the picture I think.