WhatsApp doesn’t have the same dangers that other social media does. There’s no algorithm pushing unwanted fantasy and entertainment on you. However, there are major problems with it that I fear in general the bad outweighs the good. So many “in-groups” that specifically exclude people. Lashon Hora and fake news gets around much faster. I’ve personally experienced multiple issues directly related to WhatsApp.
I can’t speak for podcasts, I don’t really listen to them all that much. However, I think they are wonderful. Just like Rav Avidgor Miller’s talmidim and Rav Frand (L’havdil) pioneered taped shiurim so that people can listen to Torah anytime and anywhere, which then exploded in popularity so that you can find tons of shiurim, speeches, and insights sold in cassete tapes in every kosher pizza shop and shtieble. Podcasts are the same thing in a different form.