While I agree with you, there are some instances where there are both tell-tale signs that a player is out of his depth and a history of him not cutting the mustard at similar levels in the past.
I personally know a Bradford season ticket holder who told me the day after we signed Seedorf that he was a terrible footballer. I think he played something like 10 games for them, and my friend said he was "incredibly quick over distance, can get off the mark like a bullet, but isn't a footballer." His opinion is that Seedorf is more of a runner than a footballer, saying that "his control is terrible, his crossing is shambolic, and he isn't made for the physical aspect of the British game."
Those quotes come from a text that I was sent the day after he signed.
He also said he wasn't all that impressed by Devante Cole at Bradford either, claiming that he's "rubbish."
Now, I know we can't really look solely at what a player has done in the past to make up an opinion on them, but I have to ask, what exactly is Robinson and his management team basing their assessments on before they sign these guys? Do they have them watched by our scouts? Cole played something like 16 games for Burton Albion last season, while Seedorf played nine games in the Spanish 3rd tier.
At least Hylton and Sloth have been playing games regularly, so theoretically our management team could have actually seen them. But the other two? Especially Seedorf? I don't know where the information could come from to sign them.