AppConnect is Insightly's built-in automation tool: you drag together triggers and actions between Insightly and a handful of supported apps without writing code. It's genuinely useful for simple cases, create a task when a deal reaches a stage, post a message to another connected app when a lead comes in, that sort of thing.
It stops being enough the moment a workflow needs logic AppConnect doesn't support: a calculation involving more than one field, a check against a system that isn't on its supported list, or a condition that depends on data living outside Insightly entirely. That's the ceiling most Insightly accounts eventually hit once their workflows get past the basics.