Only if you never need any referrals from search engines. I know a site that has this awesome locally sourced food delivery/pickup system. Connecting consumers directly with the growers.
Their site is 100% in JS. And if you google for anything even remotely close to what this site sells you simply cannot find them.
Unless you are a members only app site would I say progressive enhancement is dead. Well that is unless you care about the millions of users on slower mobile connections with crappy smart phones.