a) Dissatisfaction: Thats true - and the only reason is that you just _cant_ build a working dating website, if you could you would run out of users immeditately - but since you cant, there is an opportunity. Why you cant, is very easy: The #1 factors relevant for relationship cant (by today) picted by/through a dating app, unless everyone is able to analyze the own genectic setup and uploading it to a DB, its a random-luck-game for every participant, since you can master chemistry between two people in an "app" (or website, or service)
So dating sites/apps are selling dreams, and the owners know this very precisely - thats the reason why there is no innovation: How would you innovative a product to make it better if there are some "technical" limits on how "best" your product can be?
b) a "decent sized list" is ... do not get me wrong ... bringing you nowhere: As Markus Frind, POF founder, famously said: If your app has less than 100k active users, this means nobody likes it. My experience is, depending on target area (conutry? city? local community?) the number of 100k is by far too low - its rather around 500k-1m users - AT LEAST
c) In my country, there are some fo these "hyper local" oriented dating websites, mainly for "special needs", these are the incumbents, and most of them are on the market since 20+ years. And for sure: They also have only a search form and a userdatabase to whom you can chat.
Its not blocked in a sense that they are activly working against new entrants - its rather the fact that most new entrants cant survive long enough to get brand & traction awareness.
Trying to launch a successful (niche)dating app with a marketing budget below 50m is going to fail, I promise.