Winning the Europa League title is quite impressive especially Tottenham who have never won a trophy but it is true as you said if you look at the overall performance of Tottenham last season was not impressive and indeed they need to make big changes and I expect there will be many quality players brought in by Tottenham management.
The first step Tottenham took was to change their coach, it turns out winning the UEL doesn't make his position safe
The next step is to release players who have minim contribution Richarlison, Sergio Reguilon, and Alfie Whiteman
Tottenham's latest plan is to target players on the list but don't expect expensive players to be on the list.