Experts in relegation imply they are really good at it, and are able to consistently do it, so let's take a look at some of your list:
Pickford - Relegated once 16/17; Joined Everton 17/18; England's no.1 GK
Gueye - Relegated 15/16; Joined Everton 16/17; sold for £30m; 5 trophies and 1 UCL runner up in 2 years; return to Everton for £4m
Danjuma - Relegated in his first season at Bournemouth 19/20; joined Villarreal 21/22 became top goalscorer and reach UCL semis
The rest of these players have been relegated once and you can hardly blame individual players for a clubs relegation. Leeds had Ted Lasso as a manager for half a season and Southampton hired a manager on work experience