If only it was that simple.
But as mentioned ETH has done well at other clubs and then Ajax. At a time when clubs like Chavski, Citeh, Barca, Liverwank, Real etc are miles ahead of the normal clubs, Ten Hag has made Ajax compete with big clubs.
Yes he has been helped by having talents like De Ligt, Onana, De Jong etc. But this guy takes players, finds the right formation, plays them to their strengths and makes a better club.
At present no manager is going to succeed at Spurs due to the boardroom interfering and the politics at the club, but the best option is an adaptable manager who has more than one system in his head and can switch between systems.
Notice the way ETH can switch his defence around depending on the opposition. We've a manager who plays defenders based on a lucky dip.
For all his faults, ETH has some major, major pluses.
He's not an ex-Chavs manager and he's not Portugese.