I'm looking to develop a website. My current plan is to use ASP.NET Core 5 web api for backend and React for front end. But not long ago I hear of Next.js and that it is capable to have all backend inside Next.js. If so, is it still worth using .Net + React (or some other combination of frameworks).
Knowing the requirement of the website and the resource you have will help you find the best tech stack.
If you are very familiar with ASP.NET
and some Javascript, but you are eager to build a website quickly, I will suggest you to go with your first plan, even vanilla Javascript or jQuery for the front end side.
In the other hand, you are willing to learn Javascript deeply and try the most famous React.js Framework Next.js, and you are not in a hurry to build this website, I will suggest you to use Next.js for both front end and back end, it is stable and community friendly that you can discover a lot of resource.
My personal opinion: Next.js. It's so easy to use if you already know React. Its backend abilities are awesome, with better support for SSR (server-side rendering) than any cross-language framework combo could do. It's fast, reliable, and can tightly integrate with any backend you could want. If you're also really set on .NET, you could create a .NET backend and use Next.js to make the API calls and server-side render the results for better SEO. I've used it multiple times, and it has never disappointed. However, as a disclaimer, I've never used .NET, but I love React.