The replacement for those technologies is arguably javascript. WASM is more focused on performance by providing less abstractions and an instruction set closer

The replacement for those technologies is arguably javascript. WASM is more focused on performance by providing less abstractions and an instruction set closer to assembly (hence the name). The issue with those older technologies was that the runtime itself was a third-party external plugin you had to trust, and they often had various security issues. WASM however is an open standard, so browser manifacturers can directly implement it in browser engines without trusting other third-parties. It is also much more restricted in scope (less abstractions mean less work to optimize them!) which helps reducing the attack surface.