If you want to eat at the more popular restaurants, yes, you need to make ADRs 180 days out or you may not be able to get a walk up reservation without a long wait, if even that. And as I previously posted, Rainforest at DTD is typically busier than the one at AK, at least in my experience - we've done both and now do AK since it is less busy.
Yes, I called Disney Dining one night on the bus over to DTD to make a reservation for that evening at Raglan Road since the app was being its usual glitchy self. Was told by Disney Dining that after 9PM, the dinner rush is over and I should be able to get a table at Raglan Road with no problem - it was about 8:30 when I called. Silly me, should have known better. Walked up to the check in desk, asked for a table and how long the wait would be. After the girl STOPPED laughing, she said about a 90 minute wait. When I told her what the CM at Disney Dining told me on the phone, she started laughing again - and asked if we wanted to wait 90 minutes for a table. "And yes, ma'am you can sit at the bar, but it appears the bar is full". Lesson learned. If I want to dine at a popular restaurant, need to make that ADR before our trip.