No, that is false. It is akin to arguing that Christianity must be true because 2.4 billion Christians can't be wrong. The fallacy is easy to see because the argument can be applied equally to the world's 1.9 billion Muslims and 1.2 billion Hindus and 500 million Buddhists, etc. And yet these groups hold mutually-exclusive positions and so at least N-1 of them must be wrong.
Humans are social animals. With only a few exceptions, we tend to conform to the group. That tends to make us get stuck in very deep ruts. "Everyone is doing it" is absolutely no indication that "it" is a good idea.
[UPDATE] A lot of people seem to be missing the point here, so I feel the need to clarify: I'm not saying C++ is analogous to a relgion. I'm using the exclusivity of religious belief just as a short-cut to show that it is possible for large groups of people to hold false beliefs without getting into the weeds of which of those beliefs are actually false. The point is not that C++ is analogous to a religion, just that "adoption by millions" is not a valid argument for its merits.
[UPDATE2] I am also not saying that religion has no value beyond the truth of its objective claims. I am only saying that (some of) the world's major religions do make objective claims, some of those claims are mutually exclusive, and so some of them must be objectively false, and therefore it is manifestly true that large groups of people can hold objectively false beliefs, and therefore the fact that large groups of people hold a position is not evidence that that position is objectively true. Being "fit as a general purpose programming language" is an objective claim.