Gamification means taking the machinery of games, points, streaks, badges, levels, progress bars, and bolting it onto things that are not games. Your language app's streak. Your fitness ring closing. The little number that must go up. It works because brains like immediate feedback and hate breaking chains, and designers know it.
Is that good or bad? Wrong axis. Game mechanics are an amplifier, and the only question that matters is what they are amplifying:
Whose goal does this mechanic serve? A language streak pushes you towards something you chose, learning a language, so the manipulation feels like a favour. A banking app that instantly rewards every card payment is pushing you towards something its revenue chose, spending more, dressed up as generosity. Same psychology, same dopamine, opposite ethics. Aligned with your goal: engagement design. Aligned against it: extraction with confetti.
Once you have the test, run it on the sneakier specimens. Loyalty points that expire if you leave are not a gift, they are an exit fee built from loss aversion. A social streak between two friends is loyalty engineering wearing friendship as a costume: breaking it feels like letting a person down, and the app collects the daily opens either way. None of this is a conspiracy theory, it is documented design practice, and learning to see it is part of what the field teaches.
A rule worth stealing
A working designer's version of the test: before shipping any game mechanic, write one sentence naming the user's own goal it serves. If the sentence cannot be written honestly, the mechanic should not ship, and the fact that it would probably work is the reason not to, not the reason to.
Pick one app of yours with streaks or points and audit it with the one question. List each mechanic, name whose goal it serves, and give the app an alignment verdict. Duolingo and Snapchat produce very different report cards, and working out exactly why is the whole lesson.
Search "meaningful gamification" for the case that mechanics can serve users, and read the annual industry surveys on how developers actually feel about engagement features. Both sides of the argument are worth hearing before you pick one.