> Until you’ve hit product market fit, you shouldn’t build anything other than what is unique to your product.
How unique is your product really though? If you're a biotech company or something that also needs a website, sure, use whatever the most widely used framework is at the moment. But I feel like most of the focus of these discussions is on web-native SaaS companies whose entire business is on moving some well understood commercial activity onto the web or competing with other well-established web businesses from the huge tech companies. Stuff like e-commerce, productivity software, social networking tools, developer tools, financial tools, insurance tools, restaurant booking, hotel booking, doctor booking, etc. These companies probably feel like they need their edge to be things like development velocity and unit economics (e.g. no human customer support), and they probably feel like the only way to do that is to have a bespoke development platform.
A decent rule of thumb I follow: If there's a gem/plugin/package that could do something I want in my product...use it. Don't write the code yourself, unless it actually straight up can't provide the UX or capability you need for your product.
It's hard to argue with a rule of thumb that broad, but I think it's too broad to be useful in practice. You will still always need to make case-by-case decisions at your own discretion, and the rule of thumb will be unnecessary in uncontroversial cases (you probably won't even consider writing your own code to format a number as a string on your website) and will easily be ignored in other cases ("yes, we could just build our homepage and merch page in Squarespace, but we're going to want total control over that entire product so we're going to build it ourselves").
How unique is your product really though? If you're a biotech company or something that also needs a website, sure, use whatever the most widely used framework is at the moment. But I feel like most of the focus of these discussions is on web-native SaaS companies whose entire business is on moving some well understood commercial activity onto the web or competing with other well-established web businesses from the huge tech companies. Stuff like e-commerce, productivity software, social networking tools, developer tools, financial tools, insurance tools, restaurant booking, hotel booking, doctor booking, etc. These companies probably feel like they need their edge to be things like development velocity and unit economics (e.g. no human customer support), and they probably feel like the only way to do that is to have a bespoke development platform.