This CRM is as simple or complex as you want it. So far I have yet to find a complicated task that it could not automate.

Leads management, opportunities handling and making effective sales pipelines

Its UI is one of the best I have seen. It needs some more optimization but it is very good. It has most of the things you want from a crm and everything is connected. For example A ticket is associated with a service contract and an account. You create mails, tasks for this ticket and so on. Very good Integration with Caldav and CardDav. The github issues is the best way of solving most of your problems with the crm. There are a lot of good guys there who are willing to help.