> The plug-ins being a mixture of free and proprietary that can't be easily extended to add features
This is not true - while there are paid (“premium”) plugins in the WordPress ecosystem, they are all open source, as they are classified as derivative works of WordPress and hence the GPL virally applies.
There are in fact some plugin resellers who sell bundles of premium plugins under the GPL - it’s frowned upon by the community, but it’s certainly legal. (At least for the copyright; trademarks are a separate story.)
Typically, with paid plugins you’re paying for access to the download system (making updates easy), and for support.
My point is that the client has been given a mixture of plug-ins, some free and some licensed. Not all are designed / architected in a manner to be modified or extended. It can be a mess.
The plugins don't always upgrade easily or work well together in the future.
Wordpress is ok for some situations, I'm not against using it. I've seen enough times where it's been used and another solution Django or Drupal may have been a smarter long term option.
This is not true - while there are paid (“premium”) plugins in the WordPress ecosystem, they are all open source, as they are classified as derivative works of WordPress and hence the GPL virally applies.
There are in fact some plugin resellers who sell bundles of premium plugins under the GPL - it’s frowned upon by the community, but it’s certainly legal. (At least for the copyright; trademarks are a separate story.)
Typically, with paid plugins you’re paying for access to the download system (making updates easy), and for support.
See also, https://wordpress.org/news/2009/07/themes-are-gpl-too/