> Often this ends up as a big mess

Care to give us a concrete example? Maybe I'm misunderstanding your point here, but my experience has been somewhat the opposite. The tight integration of the Microsoft development tools (for example Visual Studio, SQL Server) is what makes it such an appealing and easy to use development platform for so many enterprise developers.

> a decade and 1000s of devs can also introduce many new flaws with each update.

I find that silly - what are you basing that argument on other than anecdotal evidence? Using that same logic you'd expect linux to be extremely flawed since so many developer's hands touch it.