Nothing like offering a freedom to post whatever you want and ripping it away. They should definitely see people being super upset at this, as some people have built their entire lives and gaining a following on using the site through NSFW blogs.
It's a step backwards tbh and I can't imagine that this is gonna keep going over well. That community's a huge part of Tumblr, isn't it? It's not like the site was ever too child-friendly to begin with anyways, a huge majority of blogs on there in general are aimed at adults and teens from what I understand. There's far more important things to fix on that site than drawn lewds. You already got safe mode automatically on and NSFW tags that you gotta go out of your way to find, don't remove the option of uploading there and ruining people's hard work in the process of trying to fix this (quite frankly, irrelevant) issue???