"but if you had practiced lean software," and "have you even tried it for real?"
sure. I have (and your assumption otherwise, as evidenced in your "if only people knew what they were talking about" opinion is revealing).
Here is a war story fwiw I didn't decide the methodology on this project, I was just part of the team - (the only "methodology" I believe in for sw dev is "hire bright people and let them figure it out")
On this particular project,there was a "lean and agile coach" (who had a PHB backing his efforts) who had a card wall where he monitored the "work in progress" and "queue size" and so on. It was obvious he had zero manufacturing experience, had never seen a real assembly line (or work cell or kanban card) and had just read this stuff up in the 'lean software' books (the authors of whom, in common with the agile gurus have zero credibility as devs or product designers) .
As expected, the project ran into trouble, the devs revolted at being treated like assembly line workers, the "coach" eventually got fired (along with the middle manager who mandated the change) and the team went back to their previous "we figure what makes sense to us and fits our environment " 'methodology' and software delivery improved, the clients were happy and all was well again. The lean terminology is a source of team jokes now -eg: "I just visited the bathroom to get rid of some muda", "Anyone monitoring he WIP for a coffee?"
And oh yes I expect to hear the "No True Scotsman" defense. "That wasn't real lean software. Hire me and I'll tell you how to do it 'right' ". Right.
The more important point is, without experience in both manufacturing and software dev, it is terribly easy to get carried away by stories about Toyota's success in car making (and the 'lean software' authors and consultants are careful to sprinkle Toyota anecdotes throughout their books and slides - none of them have worked at Toyota afaik) and adopt random elements of their assembly line processes, (or to be more precise, what you THINK is happening in a Toyota factory) into your sw dev.
"cleverly tailored" my ass. "Cleverly marketed" is more accurate. Any successful "tailoring" would need the tailor to be an accomplished expert in both sw dev and lean manufacturing and be at the top of their game in both fields - a combination of Linus Torvalds and Taichi Ohno. I am not sure such people even exist.
What we have are consultants with mediocre dev skills and zero manufacturing experience who scramble from RUP to agile to lean software to whatever-fad-is-next and are always looking for the next fad to ride, the next book to write, and the next conference to speak at.