[Garr]

Sure, he doesn't "need" a modern stack but the advantages of learning one outweigh any other option, especially in the pursuit of knowledge. React/Vue/Angular will not only increase your productivity but will teach you new and important techniques which will be a huge benefit to any future in web development.

• New tech is often designed around the idea of both scalability and maintainability. It is very easy to build large applications in React Redux and not get lost.
• Initial load times are extremely optimised and quick. Serving a bundled React file will use hardly any bandwidth and it will only happen once implying you design your UCP around using a RESTful api.
• The ability to use ES6+ loaders is a must in itself, the new features make async implementation a breeze, along with a ton of other cutting edge principles like object deconstruction etc.
• Although you can create a compelling user experience with PHP and HTML, nothing will come close to responsive SPA. If you want a snazzy animated UCP which is easy to update and adjust then frameworks are your friends.

If you're doing raw queries and echoing HTML in the same file while wanting to take web development series then you need to stop. Oh, and as Southclaw said: TypeScript. Not only will it catch 95 percent of your errors, they it also help you write cleaner code. JS if very nuanced which makes spaghetti code common and TS will help avoid that.