Skill Point Rewards from completing Quests don't apply to shield :(

[DoubleEcho]

The fact is that we were spoiled pre 1.18 with linking leves. That is what got you the bonuses you speak of, and that's likely why you see this as a nerf. It's the same way that people see THM as nerfed when it was overpowered in the first place.

Edit: To add to this, if you're worried about your SEN rank and missing bonuses, you should be ranking up CON/THM anyways with a shield. If you start at R1 CON/THM and go grind mobs you'll gain SP for both classes (main and Sentinel) at the same rate, and you'll get a higher rate of SP from 1-20. You could gain more Sentinel ranks faster ranking both classes to 20 than you could grinding mobs in the same time with your GLA. There's your bonus!