I think ENIC did more than just "ok." Considering where they started from, I reckon they did very well. And compared to clubs that have about the same potential as Spurs - Newcastle, Everton, Leeds - they did very-very well.
Success is not guaranteed - even for bigger clubs. F.ex. Liverpool didn't win the (new formate) EPL until 2019-20, and never won it with Gerrad & Carragher in the team (I know they won the CL). Woolwich went from being one of the best clubs in Europe for 2 decades to become a mid-table team.
But, yes, I agree that it seems as if Levy & Lews have taken Spurs as far as they can; and now seem unable to take Spurs further.
Each time Spurs were about to cross that "line" they backed down from making, and carry out, the necessary and vital decisions that could have pushed Spurs even further forward - hoping and believing that the status quo will be sufficient.
At the beginning of Levy's era, his tactics/tricks in the transfer market often lead to favorable Spurs deals - but then he was found out, and it worked against Spurs. While Levy, seemingly oblivious to the fact that he was found it - just carried as usual. That failed Grealish deal was the epitome of those Levy tactics.
Appointing outdated George Graham was a terrible and horrible first decision, which Levy, fortunately, realised quite quickly and kind of corrected.
Jose, though a bore, did win things. And he's got a winner mentality. And he took Spurs to their first domestic final since Ramos (2008). People say he was a failure at Man Utd., but he won 3 trophies in 2 seasons with them. What Jose did as Spurs was to expose the lack of winning mentality among the players and the board.
However, I despise some the, well, errr "names" Levy's been called, as I firmly believe he, Levy, deserves more respect than many fans give him.
But, yes, the disastrous manager search (with no set profile of whom they wanted) showed Levy & co. had lost the plot.
I personally would also like to see a new owner come in but not just anybody with money. I don't envy some of the big clubs their "blood money", despite of their success.
To me, though, I hold Lewis at fault as much as Levy. Lewis hardly attends any Spurs game and seems totally uninterested in the club, while Levy at least appears to be passionate about Spurs as a club. In fact (and I know many will disagree with me here!) I would not mind see Lewis sell the club (to more free-spending and ambitious owners) but keep Levy as the chairman, but reduce his dircet involvement in football matters.