If they believe in that core then they are wrong.
Their best players are Slay, Kelce, Johnson, Cox, Graham, Brookes and Ertz. Every single one is over 30 and the latter will be cut/traded any day soon. They need the WR who is on the board at 6 to give Hurts someone to target and replenish the rest of the roster with new talent. Watson would be great, but no point having a top QB with nothing around him and limited chance to build that when you've given up your best draft capital for the next 3 years to get him. It also doesn't make sense for him