Magic and Patrons
You can adjust the tone of a campaign by changing the source of magic. If you want a science-fiction example of this, think FTL. By going with hard physics (no FTL), you have a different feel from star gate FTL, which is different from naturally occuring jump point FTL, which is different from anything goes Star Wars/Star Trek FTL. It appears to just be chrome, but the setting assumptions this changes have repercussions through the whole mess.
So, magic. Standard (5th edition) D&D magic, you have divine casters who get spells from gods, spirits, belief in the divine, whatever. Wizards cast arcane magic through study, memorization and formula. Warlocks are gifted magic from a patron, who then requires forms of service and obsequience. Sorcerers are born from magic and control it innately. Druids and rangers practice magic through being in tough with nature and the natural world around them.
Let’s focus on one source of magic, patrons, and see how that affects everything. Patrons are the only source of magic. A cleric or paladin receiving magic from a god? Form of patronage. Sorcerers are decendents of the patrons, some of whom are locked away, unable to interact normally with reality. These are either now embedded into the world itself (nature magic), or are granting pacts with humanoids to change the world for their benefit (warlocks). But the patrons hate wizards, who use formulas to steal magic from the patrons themselves, believing they’ve tapped into an hitherto unknown source of arcane power. The rise of the wizards is killing the patrons one by one, until only the patrons outside of the world, the gods, will be left. Unless the wizards are able to tap their power as well…a war is coming, sundering caster from caster and rending adventuring parties from within.
So maybe that’s over the top, and would be a better story than campaign for play. Unless, and this is a big unless, your players enjoy that sort of thing.