Thin clients with 2007-era javascript interpreters as the only code execution framework (vs local MACH-O binaries) does seem to be a bit of a weird choice if "slow" was the problem and you intended to have thin clients.
There's also a backend. Back in 2007 a web app was mostly backend code that would send you HTML to display, and at worst it would have some AJAX for a chatbox/autoreload.
Read that again to yourself, slowly.