None of us can really say if Morata is great or average, since we've all seen way too little of him. If Conte goes as far as calling him a great player, then he probably watched the boy much more than we have, especially at u-21 level.
As with most young players, we'll buy potential at this point, with no security at all regarding his future development. Well, that's our only chance to get our hands on world class players, because we can't buy an established star. Sometimes we'll hit the jack pot, as it happened with kid Pogba and the young(ish) Vidal, sometimes we'll miss. It remains though that the reality is as it is - we can get world class players only if we get them young.
As far as Morata goes, we can just analyze the stats, and they talk about a player who's really dominant at his level. He was the topscorer at both the U-19 and u-21 European cups and has an average of more than one goal per match for the u21 (13 goals in 12 matches). Even more, at the u-21 Euro he was 2-3 years younger than most of the others. At 20, he outplayed guys like Immobile (23 at the time), Destro (22) etc. In Real, last summer they had enough fate in him to sell Higuain and use Morata as the only striker in the team in addition to Benzema. He also has some crazy 1 goal in ~70 minutes record in Madrid. It also says a lot that Real insist on a buy back clause.
Like I said, we're betting on potential here, because that's our chance to have world class in our team. Morata proved his superiority at the level he played so far, but he's yet to prove himself at senior level. The Juventus people clearly think that he has it. You say he's a random player, but that's not quite true. It's the boy who proved to be more potent than any other European kid his age.