Technology choice is by far the least important choice. A business is seldom about technology, but the value for customers. Other factors count more, but your question leaves all important factors out. So the consultant answer is: it depends….

its an ms thing and how much does one want to be at the mercy of an ms roadmap

Anti-MS sentiment is common in some corners of the tech world. People ignore the fact that the CLI and C# are ECMA standards like JavaScript and C++, and treat them like closed proprietary systems. .NET is a great choice and there are tons of people who happily use it.

A) It used to suck

B) It's not that popular for frontend, which is a very important concern for most early startups

C) Microsoft was historically only used because it was Microsoft, not because it was the best choice

It's mostly a Microsoft brand problem that they rightfully earned by being bullies producing over-complex, stagnant corporate IT trash.

Because it's shit

I love it. Been using it professionally since the beginning. I owe my entire career to it.

This year, I've switched to Go for all projects moving forward, and will never recommend anyone ever touch anything MS has any part in.

Historically it was targeted at already captive clients building on Windows, so there was no incentive to innovate or break eggs. This persisted just long enough for the industry to evolve (web & Linux) and create much better solutions, making MS’s dev tools largely irrelevant. Today, seeing .net in a shop is a red flag for me at least (choosing .net for Web work, to clarify)

Startups need to move fast to quickly validate their assumptions. Full stack batteries included frameworks like rails, Laravel and Django are much better suited for this with integrated background jobs, mailers, authentication and authorization, caching, queuing, notifications, active record style ORMs and broadcasting systems all baked in and designed to work together not to mention a common project structure for all apps and built in unit, feature and integration testing infrastructure. Add to that a huge ecosystem of packages designed to integrate with the framework and a large community.

I personally use Laravel for my side projects and but have been a long time asp.net user at work where working with multiple teams on large projects is more of a concern.