Trying to save money and time by going with a pre-made solution is going to pay you back with frustration later. Best bet is to always build from scratch or build from available components that you can configure the way your particular software needs to work. I would look to open-source javascript frameworks like Meteor JS which is made for rapid development and has access to a huge ecosystem of pre-coded libraries and components for just about anything you need.

Honestly the tech you use is far less important than how you can attract users. The value is going to come from the people. That being said as long as the platform lets the community interact with each other freely you should be fine.

We can hop on a call if you want to go into details.

Use WordPress + you'll save yourself many headaches.

Try a combo of WordPress + Paid Memberships Pro + if you're also providing courseware, WP Courseware.