Setting aside the fact that I think entrenchment is a reasonable definition of success, I imagine most hackers don't judge a technology's success based solely on that metric.
As a dumb example, if a language fails at its stated goals, then that's not successful. Another dumb example might be a language which tries to incorporate FP patterns but implements lambda syntax or semantics quite poorly.
That’s true. But most languages fail at their stated goals to a certain extent, usually by finding an unanticipated niche in which they thrive. What a language is good for is often something you discover, not something you design.
As a dumb example, if a language fails at its stated goals, then that's not successful. Another dumb example might be a language which tries to incorporate FP patterns but implements lambda syntax or semantics quite poorly.