Small, 20 people maybe, but a lot of remote people that had their own small "domains" within the project. Sometimes one "domain" had multiple shifts (e.g. shipping). Communication between shifts was just done by writing yourself an email.
Granted, such a thing would not scale up to infinity, but for that size it was perfect and extremely hackable (just email + SMTP after all).
Generally speaking any organisation, given enough time, can establish processes that are better than JIRA with a certain amount of luck.
However, that's the best case scenario.
It's a standard distribution. Sometimes a 100 person project gets by fine with email. Sometimes it all goes to shit.
A tool like JIRA is, on average, a lot better than doing it via email only.