I would argue that private equity has had a longer deleterious effect on product development, and also some IPOs have turned out disastrous, but it isn't a hard and fast rule to say that a company, once it goes public, automatically turns against its userbase.
I paid for it recently. So far it's been a mixed bag for me. The core works as intended, but little annoyances can add up.
I love that the design is small and light, but almost none of the languages is use are supported by Pygments for highlighting so someone browsing the code may find it off putting (GitLab I can use gitattributes to select a different but compatible Rouge highlighter). I like that NixOS is a first-class compatible image, but GitLab offered more in build options (run certain tasks only on tags, run this job on a cron, etc.). I love that I can push any markup I want to the ‘README’ of a project, but I wouldn't have to if Markdown wasn't the only option (MD's so limiting without admonitions, definition lists, block titles, ToC, etc.). Project discovery has a lot to be desired, but at least it doesn’t have gamification like “stargazers”.
In my opinion public exit has been twisted 180 degrees. The reason for a company going public is to raise capital that individuals do not have to expand the business - build new factories, hire or whatever. After all there is much more money distributed in the public than few individuals have and in exchange you get shares in the company.
I don't think GitLab is in need of that, what a lot of companies are doing now when they go public is just a method of 'cashing out'. When you have a great product as a private company your income comes from the users and you tailor and improve your product for their needs. When you go public in the above sense you're cashing out and suddenly the users shift to a product and shareholders are now what you cater for while trying to milk your 'users' as much as possible without them quitting.
While it's true sometimes shareholder interests can lead to the users getting screwed, that's a very short term and dangerous game to play. It's the equivalent of killing the Golden Goose. Companies that play that game may find themselves out of business in short order. They're opening opportunities for the competition.
