For me there's 3 issues, which are not just limited to the first team squad, but can be put on the whole of the club.
Mentality.
Now you can throw all the other words you want into this category, heart, fight, too nice, winning mentality, bottlers, losers, passion etc. This goes throughout the whole of the club, under Kenwright & Elstone they did the bare minimum commercial wise to be successful off the pitch, that seems to be changing now which is great. On the pitch though as highlighted by
@GrandOldTeam article it's been a problem for years. Now many of us have probably seen the Spurs documentary and Mourinho telling his players to be "c star star t s" on the pitch, that's what you have to be to be the best and win. The very best elite sports(wo)men are all the same, they're generally horrible to the opposition in their environment.
Now I'm not meaning to pick on anyone in particular or be blase about mental health, particular mens' health as it's a big issue, but we have players who are either mentally weak or have issues. Micheal Keane and Bernard have both publicly talked about their issues, which is great they have spoken out about it. I have a sports science degree, my diss was about early signs of burn out, I know how effective psychologists can be in improving a persons sporting performance. Now if you want to win and be the best, unfortunately you can't have any weakness.
This came up a few weeks ago during / after the Real Madrid - Chelsea Champions League ties.
Toni Kroos doesn't lose sleep out of disrespect, he doesn't lose sleep because hes confident in his own ability and the job he has to do. The very top players have this attitude, James and Allan will probably be the only ones in this team with it. Micheal Keane could be the worlds best defender both physically and technically, but if he's up the night before a game worrying about how Callum Wilson ran him all over the place in November then he's not going to perform at his best when he faces him for the reverse fixture. Which evidently is exactly what happened and unfortunately if you want to be a the top, win leagues or cups that mental weakness will really cause problems. I imagine a large number of our squad are like this, but also there will be some who equally don't lose sleep because they're really not that arsed.
Improvement.
Why do none of our players actually get better? Before anyone lambastes me let's start with the obvious. DCL hasn't improved as a player, he's been told by Ancelotti to stay within the width of the goal posts and try and in the box as much as possible, because his strengths as a player are aerial and one touch finishing. Why hasn't his touch improved, his dribbling or his ability to kick a ball outside of the box? Seamus Coleman has never been able to cross a ball, he's the exact same player as he was in 2010. He runs on the overlap, can run back, puts in a good slide tackle and can shout in a high pitch voice. His fundamental problem has been his crossing of the ball and it's never improved. We had one of the best crosses in the league in Baines on the other side of the pitch and now in Digne, why hasn't he spent hours practicing with them to get better? Holgate was actually looking really good when he first returned from injury but he's been getting worse and worse as the season has gone on, he has over 100 appearances but he's probably worse than when he joined. Tom Davies has nearly 200 appearances and nothing has changed other than he's fitter and runs around a bit more. Richarlison is literally the same player (albeit worse this season) as when he first appeared in the PL for Watford. Not one aspect of his game has improved, he hasn't become a better finisher, passer, dribbler he's just the same.
Footballing intelligence.
In basketball 'basketball IQ' is a massive thing, american football is similar but football it's always used in isolation. A striker has "great movement in the back", a midfielder can "see a pitch forming in their head before others", a defender has "great anticipation to block a shot" etc. Oddly it's never encompassed as a whole for football as 'footballing IQ'. Taking it in the broad sense all of our players apart from James (because he's world class) have just terrible footballing IQ.
A lot will be brought up during a game about Richarlison and his poor decision making when it comes to passes and that's because he has a low footballing iq, he's absolutely brain dead.
We see it so often with Holgate and Keane passing from the back, Godfrey taking that crazy shot from outside the box and Carlo just shouting "why?" at him. Players turning back towards goal to pass, not making forward passes or driving forward with the ball to attack the opposition and put them on the back foot.
Obviously better players would have better intelligence but that's up to Brands and the scouts to recognise it.