ASP.NET Web Forms “just works,” but for sure it encompasses design principles for web applications that are becoming more outdated every day. You can still build web applications using ASP.NET Web Forms, and you can still find and buy plenty of commercial libraries and tools. The platform is mature and reliable and, although it won’t likely receive more treatment in the future, it won’t die overnight either.
You might have read, or you might even think yourself, that any product that has not received updates for years is a dead product. Well, that depends. An absence of improvements certainly shows that a role is no longer considered to be strategic. But a lack of improvements also indicates there’s no more to add without rewriting the product from scratch according to new principles and a more up-to-date vision. Yet, the old product works.
It’s like a TV a few years old. It won’t give you the best experience, but you can still use it to watch your favorite shows. You can get a new TV, but you shouldn’t be too critical of those who don’t. It all depends on how crucial it is, business-wise, to jump on a new platform and how much it will cost you. Web Forms is obsolete from a design perspective, but it can still let you quickly arrange solutions with its own tools.
Similarly, you might encounter difficulty if you need to ensure full accessibility to all pages of the site or if having SEO-friendly URLs is critical. The requirements of the presentation layer—responsiveness, gestures, and touch-first user experience in particular—are other possible sore points.