Someone doesn't really need a reason to build something besides that they want to build it. I built many RSS readers and I was not trying to revolutionise anything, I was just having fun. This mindset of "revolution" and "disruption" will block you from actually just doing the things you want sometimes.
I guess it depends on the goal. If you just want to build things then you don’t need anyone’s permission, but if you want people to use it or to make a living off it, it’s important to know why people would use what you’re building.
One of my soapboxes is that the world is full of really smart people trying to solve solved problems for the sake of having done something that feels like something. I advocate for people taking that creative energy and pointing it at partially/poorly/un- solved problems.
If that's developing to offer (OP in particualrly said their friend would soon be offering a new service) an RSS Reader because there's something to actually innovate and more fully solve a problem, then it's great. Otherwise, it's just fodder for AdWords and Facebook when they eventually try to build acquisition for a business around it.
