I feel that it wasn't made to host enterprise products but rather FOSS in competition with GitHub and then made a pivot to enterprise products but not quite moving away from the "this is for FOSS on the web".
Things like "can modify own comments" not being something that can be modified (people updating their own comments and then not being able to go back over it for an audit or information request of some sort) or having a manager role that can administer the members of a project but not the code.
And yea... having to pay $100/month for a product/project manager in a larger org is a rather firm "nope." Have a dozen of those and that's a lot to pay for not much functionality.
A previous company that I worked at... there was a project manager. Just one. It was a small company - I sat across from the other Java developer. In there, were you've got a small organization where $100/month for a PM is a lot to swallow, but its only $100/month for one PM (and then you get all the other features that saves you from having to hire another operations person) - that's not as hard a price to swallow.
There the thing would be "ok, we've got 10 people at $20/month and all this other stuff that we need to set up on our own, so $200/month vs 11 people at $100/month and a bunch that we don't need to set up on our own $1100" -- the "is it worth $900 for the rest of the infrastructure done for us - along with dumping trello for gitlab issues" and the answer would probably be "yes."
For that, the ultimate tier is now competing with a Jira suite, or something that PMs use made by Microsoft or a similar type of product.
The licensing for the project management tool can easily run $50+/month/user
Add in the "business/customer access to the issue tracking" and if you've got Jira or similar, that adds on a gain a bit more $$.
Next, adding the artifact scanning tools. Yes, you can get them 3rd party... but its another thing to set up.
In the end, picture the 50-100 employee shop where the sysadmin is weighing in on "get GitLab Premium vs GitLab ultimate" and the reduction of additional installs and licenses that need to be managed.
Yea, it it adds $80/user/month, but if it saves an hour or two per user per month in productivity gains - that can make a difference.
In the organization I currently work for, we were considering the options of (GitLab Ultimate) vs (GitLab Premium + Jira + other tools) and ultimately went with the premium and other for a number of reasons... but GitLab Ultimate made a strong showing.