Because we've already spent millions on dubious transfers such as Pogba, Maguire, Lukaku, Di Maria, AWB, Fred, Matic, Mata, Martial, not all of which are flops but none have risen to the expectations their respective fees would suggest. But apparently what we were missing to win was another additional bunch of overpriced players, per the calls for additional transfer spend.
Barcelona have been the masters of that in recent years, always spending on the latest emerging star only for them to be flops for them: Coutinho, Griezmann and Dembele.