There are many applications for MIDI that don't necessarily involve rendering audio in the browser. Most useful I've found are various patch editors for hardwar

There are many applications for MIDI that don't necessarily involve rendering audio in the browser. Most useful I've found are various patch editors for hardware synthesizers. I've also experimented with using MIDI for camera control applications, where you'd traditionally use some expensive joystick. Another application is exactly the opposite of what you fear: offload audio rendering of some musical data to a well-optimized software synthesizer or a hardware synthesizer, via MIDI.