I agree with you, I just feel that terrible is a bit much particularly when you seemingly share my opinion when it comes to Pochettino himself, I don't think that he is doing a terrible job but that he reached his ceiling and his doing the best he can. At the very top the difference between good, very good and great is marginal.
If I was to give an example it would be Pellegrini or Capello at Real Madrid in the late 2000s, neither did a terrible job but they both showed their limits, neither were able to take Real Madrid to that next level. And that's what Pochettino is doing with the added twist that he isn't really good at tweaking his own tactics and make it work with different type of players, but we already knew that at Tottenham, he consistently struggled to integrate new players.
Now since this thread is about ETH, what I find very interesting with him is that he has used all sorts of players in almost all the positions, if you look at the type of players that he has had position by position since 2018, a large amount are different to their predecessors. I find it very interesting that since his appointment at Ajax, he has for example used Tadic as a lone second striker, huntelaar as a poacher and Haller as a target man. His pair of central midfielders have been made of pure DMs/former CBs, attacking 8s, defensive 8s or deep lying playmakers, wide he has successfully used all the type of players that exists the archetypes being Promes, Antony, or Ziyech.
To me that's critical because on paper he is the type of manager that can be given time because he has core values but he understands them well enough to make them work with different types of players and he tries to make it work with different types of players. I don't think that he needs or want to have 11 new players before implementing his way, in that sense he is very much like Van Gaal, Klopp or Guardiola.