Adama is one of those rare players who despite not being particularly good is probably the best in the world at doing one specific thing, in his case carrying the ball up the field at pace. Unless he improves the rest of his game drastically, it's very unlikely he'll succeed as a starter at a top team, but he has his uses. In a situation where you just need someone who can get the ball up the pitch and keep it there (to take pressure off when pinned back, or when your midfielders can't find their forward passes), or if you want your opponent to think twice about playing a high line, there's almost no-one better. It's only when he gets up into the final third and there's not a simple pass on that his limitations become clear.
I think the best comparison for Adama is someone like Fellaini - limited players who have one outstanding quality which can make them very effective in specific situations where that quality is needed and who can cause your opponent a tactical problem they're probably not really equipped to deal with. I can see why bigger teams than Wolves would want him as an option off the bench/in certain games, in the same way I'd have had no complaints with us signing Fellaini if we'd only really used him as a last resort in that wrecking-ball target man #10 role he played for Everton. If Barca are targeting him as a tactical option it's not an especially weird move aside from being a reflection of where they're at right now. If they want him to be a key player it's a shocking indictment on how far they've fallen.