It's a decent CMS
I'm an IT professional with over 35 years experience, and I have worked with many different web content management systems over the last 15 years. When I started at my org in 2019, I was introduced to the CMS that's built into the YourMembership. I've been surprised that it's actually a pretty decent CMS. They use the RadEditor for the HTML wysiwyg editor which is pretty good. There's also strong version control for the pages you create so that you can easily restore/revert an older page if needed. They offer a preview mode before publishing pages along with the ability to relate pages, enable/disable a share widget, secure pages by member type, add voting/scoring to pages, and more. The resource manager for uploading graphics and documents is also decent as is menu management. You can create and customize your member directory search and search results fairly easily. I also like that the site's CSS can be customized without too much trouble.
My main complaint however is that customer's can't create or edit a website's structure. You have to contract with YourMembership for the initial design and you have to go back to them for any major changes to the layout of the home page and second page designs. Related to this, there are no page templates to work with for different page types. Other modern content management systems will let you define page templates for event listings, a page template for event detail pages, a page template for a resource (download), a page template for major topics -- just to name a few.
A secondary complaint is that customers of YourMembership have experienced downtime over the last 9 months that often exceed more than an hour. After significant customer complaint, they created a status page that customers can check when there's an outage or significant performance problem.
But again, if YM meets your AMS needs, the website CMS is decent.