In fact, I was using VS Code on 10 year old Core 2 Duo 2GHz machine up to a year ago. Without extensions, the responsiveness was fine -- definitely not as responsive as gvim, but otherwise no complaints.

When I added extensions, it did start to feel laggy but once I turned off all extensions save one (the language server extension -- in my case, Python) it was fine again.

With my current machine (a refurbed 2014 Intel i7 Dell desktop), VS Code is pretty responsive even with extensions enabled.