abundance of the runtime, ease of distribution of programs, the permission model which was bolted on, appropriate sandboxing mechanism leading to authorisation

abundance of the runtime, ease of distribution of programs, the permission model which was bolted on, appropriate sandboxing mechanism leading to authorisation problems and performance when people were not ready to sacrifice a very significant amount for no reason. Oh, and breaking changes between versions meaning you needed multiple runtimes and still got weird issues in some cases.