A slightly different take on your “eye engagement” point is that podcasts allow us to utilize time that would otherwise be spent listening to music, talking to others, thinking, or just zoning out. Combined with Apples air pods (a horribly great piece of technology), I find myself using lots of time for podcasts that I wouldn’t otherwise (like when I’m doing the dishes). I find all of this enjoyable overall but I do worry that the decreased time that I spend in thought or present with others could be a net negative in the end.