It's occasional rather than the norm, the Arsenal game was a year ago, you're so good with stats, tell us the other occasions where he's offered a moment of sheer inspiration out of nothing.
I'm not knocking Mane btw, but the "I suggest you watch the arsenal game" comment is a typically over enthusiastic and misguided retort. It was the exception rather than the norm, unlike what Coutinho offers. If we're going to offer up solitary moments as proof, we may aswell label Henderson & Can match winners, for their rare moments of inspired brilliance, but that would be daft.
Yes but 'occasional' is good enough and what does it matter if the first example we think of is the Arsenal goal ? It's not as if Coutinho does it every other match either, he scores 3-4 screamers per season in the PL and maybe the same that he creates with magic himself in the box.
However it's not just about scoring yourself, many top 'creative' players who make magic happen, don't appear on the top scorers' lists, but there's no denying their involvement in goals, no matter who scores them. Mane could probably be on both those lists of course.
You know as well as I do that without going back and checking every goal we scored (or e.g. Mane scored at other clubs) it's tough to say how many were 'creative' (to use a 'catch all' phrase) and that the term is rather subjective in itself. So actually you haven't offered up any evidence to the contrary - merely a contrary opinion.
Anyway for your perusal (below) from Mane's 2016/17 season, I'd say 3-4 goals fall into that 'creative - did it all himself' bracket even though his creativity is different to Coutinho's for example. Behind Coutinho certainly but then most players in the PL are, but undoubtedly a player that, to use the original term used by Glen, can regularly 'create something out of nothing' and the Arsenal goal is far from an exception even if it's the most obvious example.
To use stats (goals and assists), that don't come close to showing the whole picture of course because 'involvement' or 'creativity' per se isn't noted :
Coutinho 21 in 31 matches
Mane 21 in 27
Firmino 22 in 35
Lallana 15 in 31
Wijnaldum 15 in 36
Origi 12 in 34
Sturridge 7 in 20
Mane - Liverpool 2016/17 (no doubt there's more than a handful at Southampton too but I can't be arsed checking)