Well there is specialization and hyper specialization. One is good for the game… one Imho is bad for the game. An opinion I developed after 12 years of playing Pathfinder and 3e.If you aren’t specialized, then what’s the point in having classes to begin with?
Hyper specialization trivializes challenges and often leaves the character vulnerable in other ways. It can also imbalance the party and cause friction with the DM when they either don’t allow each encounter to be trivialized or have the temerity to capitalize on a PCs weaknesses.
Wizards are cool. Wizards with spell DCs of 20+ are not fun for anyone other than the wizard. Ergo, cap Stats to 20