My choice of techstack has nothing to do with the feature list because at the end of the day it is whatever gives you an advantage which is whatever you are better at than everything else so long as it has a rich third party library ecosystem to borrow from.

For the database I would choose PostgreSQL because you can rollback schema changes which you can’t in MySQL. SQL Server would also be good but it is more expensive which it is not always supported well depending on the platform, so you would end up gravitating towards Microsoft cloud services for convenience, which can get pricy if you’re not careful.

For the application layer I would pick either ASP.NET Core/C# if I was going the Microsoft route, otherwise Python all the way for everything. I admit that I always thought Python was comparable to PHP in terms of a terrible programming language, but I have discovered that the lack of types, similar to JavaScript, is it’s power. I will say in the wrong hands it will be a disaster for a large monolithic application due to lack of unit testing and clean code principles, and static typing is a great first line of defense from a regression testing standpoint. However, if you know what you’re doing, Python allows you to build infinitely complicated software at the speed of light which is exactly what a startup needs to be able to do: iterate as fast as you can. Build the MVP as fast as possible and user test it, and then go back and unit test as much as you can and also write e2e for the main workflows. If you don’t get into the habit of doing this, or don’t foresee yourself writing unit tests, avoid Python like the plague and stick to a typed programming language. I would not use your product at least because your site is going to go down at some point because a junior dev you hired had a typo and you were too tired or busy or lazy to properly review their code.

For frontend, React. I think any framework would be fine, including vanilla HTML/CSS/JS. I would vouch for any framework that has a lot of third party libraries, although the upside of React is how fast you can build things. I’ve heard of Angular and I’m sure there is so many more, if you’re familiar with it then you will probably be fine.

I know this is a hypothetical situation, but I think in reality you would not really know what all features your users want from the getgo because you have no users yet. One thing I noticed, and I know this is more to do with picking techstacks than a discussion on product market fit, but what is the problem you are trying to solve? It seems like you have a product in mind that you are trying to find a problem for it to solve, which is not recommended. Assuming this hypothetical scenario is in present day, it sounds like you would have Facebook, Reddit, Hacker News, and a multitude of other platforms to compete with. The problem they are trying to solve is that people want to connect with other people. It is interesting to point out that they all solve that problem in similar but different ways and are better at connecting certain kinds of personalities better than others. So I’d just be interested in whether you have thought about a specific type if person you are thinking of or have met that would be better suited for your platform than the others available?