Sure, but "Tumblr is not easy to use" doesn't really instill confidence. Tumblr used to be very easy to user. Perhaps one of the easiest websites out there in terms of usage.
The underlying problem is actually two fold:
1. They didn't understand their own customers need (which was, to be frank, share porn)
2. That they quite simply lost momentum
The first one is addressable. Just say you're going to allow porn again. The second one... Well, that's harder to address.
It's hard to make legitimate money from hosting porn. Most people don't want their ads next to porn, so you either need to have sex-related ads or a subscription fee.
Twitter and Reddit have kind of built legitimate businesses on porn hosting, but they also host a lot of non-porn that makes them seem more legit. Tumblr wouldn't have that.
The underlying problem is actually two fold:
1. They didn't understand their own customers need (which was, to be frank, share porn) 2. That they quite simply lost momentum
The first one is addressable. Just say you're going to allow porn again. The second one... Well, that's harder to address.