Being a fulltime web developer with over 500+ sites in the past 12+ years, I can tell you from experience that we've used/seen/fixed/tried all these options that people have discussed and we've come back to the oldie & goldie each time in Wordpress.
Here's a couple quick reasons:
1. It has a TON of man hours into developing a platform that isn't perfect, but works better than 99.99% of all people/companies could put together.
2. It is proven and it WORKS solid.
3. There are tons of plugins that make your site do what you'd like it to do. Don't have one with a function that you are wanting? Either code the functionality directly into the site or build your own plugin and have it do exactly what you'd like.
4. It's extremely flexible to work with to get it to do/integrate with whatever you'd like.
5. It's easy to find developers to work on it since there are a lot of WP developers out there that can help you out. Some of these other platforms, if your developer leaves you, then you're sunk.
Those are just 5 quick reasons why we recommend WP and keep coming back to it. I can't even begin to tell you the number of clients that we've gotten because their developer recommended a solution or custom built them a platform, then the developer went out of business, got lost on a boat in the middle of the sea, or just completely quit returning phone calls and they left the customer out to die. Then the client calls us and has to make another decent investment for us to build them something brand new from scratch on WP. The most recent, was with a client who had their custom built platform for 3 months and the developer disappeared.
Sorry to say but these stories happen all the time. That's why we're not cheap, but we take amazing care of our clients day & night (including sending them $100 of cookies like we did for a client yesterday. LOL!)
Hope this helps. Let me know if you have any other questions.