I am not going to downvote you because that's just not my thing. But I am going to have to disagree with you pretty strongly.
You are quite right that experience is necessary to complement theory and in that regard I suspect you have exactly f^%k all experience with social workers. Now, maybe I'm wrong, and maybe you or someone you know had a bad experience with a social worker - heaven knows they're only human and thus variously good and bad at their jobs, just like teachers and doctors and nurses and IT professionals and welders and whatever it is you do.
But if that is the case then that's where you can't just rely on your own observations and where learning provides a greater perspective to understand a broader range of situations rather than the limited experience that any one person can have.
Now, my experience with social workers is that I, personally, know several, both family and friends, and have dealt with two who were helping people I knew - one a school friend and one a close family member - and can testify that those who are good at their jobs are some of the most dedicated people I know. Indeed, the experience with the two in my youth actually had me change my carrier path from IT to social work, believe it or not. In the end, circumstances changed unavoidably and I had to decline my university acceptance, and after a while I took up IT again, though that is getting off topic a bit.
It's important to understand, however, that social workers work inside a legal framework but, within that, they fight for the people they represent in ways that I doubt you appreciate; advocating for them with medical professionals, hospital and healthcare administrators, government representative, police, landlords, teachers, bosses, parents, and anyone and everyone they need to or can. They argue the rules and, where there is room, they attempt to secure assistance that might otherwise be difficult to obtain - things like extra days in a hospital beds, consideration exams at school, admittance into programs. recognition of extenuating circumstances and so forth.
They will fill out the forms at home at night and deliver them in-person at meetings and hearings, across town and in their lunch breaks, after having spent an entire weekend at the hospital and visiting clients.
A great deal of social work has nothing at all to do with parenting, but even where it does, a social worker is primarily concerned with the well-being of the person whose care they are trusted with. It is certainly true that, when dealing with a family situation (which is not universal in social work,) it is important to understand the dynamics and history of a family. What is not clear, however, is why exactly experience with one single family (your own) provides a suitable or even necessary basis for understanding the complex situations that exist in another family; keeping in mind that a social worker may have to deal with several families in a week and dozens over the course of a year - all unique with unique histories and unique concerns and problems.
And this is where theory - and training - comes in as one must know how to walk into a situation with a family who are strangers and who may even be hostile to you and to go from there to a position where you are able to not only understand the problems and opportunities but to then work with or, sometimes - regrettably - in opposition to them to achieve the best outcome.
That's not a skillset that simply being a parent provides you with, just as it doesn't provide you with the necessary training and knowledge of the (complex) legal and regulatory landscape that you must operate in.
So really, I do agree that "practice" and "experience" are essential components to the development of a social worker, but that practice is the practice of social work and that experience is the experience of the situations in which a social worker must operate.
The suggestion that social workers, trained an experiencing in social work are somehow less able to do their job and advocate and assist those in their care is as ignorant and it is insulting.
I don't know you but I hope you never have need of a social worker. But, if you do then I hope you get some small appreciation for the job they do and how dedicated the vast, vast, majority of them are and how utterly wrong you were to dismiss the level or care and concern and sheer hard work that they bring to achieve positive outcomes.