Yeah I agree that C compatibility is the fail. But it's also the only reason C++ is around today. There were plenty of other compiled systems languages with OO or module systems floated in the 80s, including the quite capable Modula-2/3s, various Pascal dialects, etc. Of all of them only C++ (and Objective-C because iOS) has any relevance today. And likely because there was a kind of path to trendy-OO for existing C programmers and shops.