I’ve worked in plenty of scrum teams where the product owner ruled the roost. And normally this was a good thing when the team was small and they played a hands-on leadership role. Just like the scrum guide says they should.
It was certainly comforting as a developer to have the product owner attend all scrum ceremonies and be on hand in refinement sessions to directly answer questions. Any over-dependence on the product owner was generally more beneficial than liability.
Where this gets problematic, and quickly, is when the product becomes more complex, the user base grows and becomes vocal about their needs, and/or the scrum team itself grows bigger. The demands on the product owner grow significantly, even exponentially.
The mistake here is to firmly believe (and expect) the product owner to remain hands-on in the same way they were in the smaller team. And I’ve unfortunately seen several product owners burn out like this.
Rather, the first line of defence is delegation and empowerment. The product owner should delegate as much (as appropriate) to empowered team members. Even certain product decisions should be delegated. Remember that everyone has a certainly level of ‘ownership’ or commitment in a scrum team.
A really good guiding vision for the product and team to work towards helps greatly as a North Star when delegating. Also, a product owner who doesn’t need to be a single person saviour, or perhaps dictator. And also the absence of personal punishments when team members can and do get things wrong in their empowered decision-making.
Beyond that, and more as a function of technical team size, appointing a dedicated business analyst and/or technical lead introduces nominated roles for specific delegation and empowerment. By this stage, expect the product owner to perhaps only attend sprint kickoff and the end of sprint demo. Not what the scrum guide says, but realistic and workable none-the-less.
None of this is easy, or straightforward, but it is certainly possible with the right commitment, ongoing communication and necessary adjustments along the way.