Think De Boer deserves a bit more credit. Not saying he will fit the bill at Tottenham but
(1) Lost the likes of Alderweireld, Eriksen, van der Wiel, Anita, Vertonghen, Stekelenburg, de Zeeuw and Suarez over the years and I think his most expensive signings is Kolbeinn Sigporsson €4.5 million.
(2) The Dutch Eredivisie not the strongest of league when compared to the other European leagues but its fairer to look at picture domestically rather than judge Ajax on their history. Won the last 3 titles by (2010/11) 2 more points than Twente, (2011/12) 6 more points than Feyenoord, (2012/13) 7 more points than PSV and gap between Champions and 3rd placed team has never been more than 7 points in the past 3 seasons.
(3) Bringing through young players, which I would presume is his brief. The team that beat Barca 2-1 at Amsterdam Stadium in November had an average age of 22.7 yo. Of the starting 11, only keeper Cillessen (from NEC) and Hoesen (from Fulham) were signings. The other players all progressed through the academy.
(4) Style of play (despite having to bring through young players and guaranteeing results to win title)