Should I pursue the idea I like despite there being some competition and me having no strong differentiators?

I'll keep it as short as possible. So I have this idea for a SaaS in the dev tools area. There are five competitors, all pretty new (\~3-4 years). Three of them don't seem to be big, and two - are (and both are backed by YC Combinator). I've been having this idea for a few years now since I encountered a problem at work and couldn't find an existing solution for it. I am fairly passionate about it, and it has a lot of qualities of a perfect idea for me: it's a potential lifestyle business, I have the right skill set, it's not that easy to replicate without the knowledge and some effort, etc. Now, every book and "startup guru" says you should just start and figure it out as you go. But somehow, this isn't very convincing. I have two big doubts: 1. I mapped out all the competitors and features they have. I cannot find a differentiator for my product... Apart from cheaper pricing and better support for early customers - I have nothing unique to offer at this point. Maybe I discover something as I go, yes, but how do I even sell as a new player on the market if I don't offer nothing apart from that? How do I validate it? (Which leads me to the next question) 2. I haven't built anything yet, simply because I fight the urge to start building before validating - as everyone is suggesting. But what should I be validating if the market exists and there are competitors? Evidently, the product has its applications and customers. What should I be validating then? That specifically MY product can have its place? It feels like a chicken and egg problem: it will be harder for me (pre) sell without a prototype/MVP because it's not like I am building something they cannot get elsewhere right now, and need to wait. Thank you.