I get what youre saying, but if you have a wall full of old, wet, moldy boards and replace 5 of the rotten ones with fresh boards worth a combined 200mill, the non-moldy ones arnt going to better the old boards, the old ones will on the other hand infest the fresh ones with death. Its not a one to one analogy, but you get my meaning. And yes, Im a carpenter.
Just to clarify, Im not saying its all Robertos fault, but he is absolutely partly to blame for Evertons state.
The defence under Martinez, across the 3 years:
Howard/Joel
Coleman/Hibbert/Browning
Jagielka/Stones/Distin/Alcaraz/Mori
Baines/Oviedo/Galloway/Garbutt
14 players (sorry if I missed any). Martinez signed 4 of them in 3 years (Plus Holgate, who I don't think made it to 1st team while he was here).
The rest were Moyes signings or youth players, 3 of whom are still regularly included in the 1st team.
Koeman came and added:
Stekelenberg/Pickford
Martina
Williams/Keane
(Plus Kenny who he begrudgingly included after 1st trying Davies and Calvert Lewin in his position).
Now, you could argue that it was Martinez not addressing it sooner that was the problem. That would be fair. He clearly decided that focusing his resources on Lukaku was the most important thing.
But looking at the defence now, as poor we are, and with only Holgate really being included as a Martinez signing, who as we know, didn't really break through while he was there, can we still really say it's Martinez fault?
Using your analogy, Martinez had 2 weak points needed fixing and only had the money to do 1. One was the front door that had panels missing and didn't close any more, the other was a back door that was much older, but still had all its panels, still managed to close and lock, but made a creaking noise and rocked a bit on the hinges when it was left wide open. After fixing the front door, he tried to patch the back door as and when panels finally gave way, and bought another new panel but didn't get round to attaching it.
The new owner of the house, got rid of all the newer panels, but kept the older ones that had now rotted further, and to make matters worse, he used partly rotten (but still expensive) 2nd hand boards to do so as well.
He also sold the front door.