What classes are being changed? Everyone you change seems to be losing something. What are they getting in return, and how are your players taking it? Do they all play fighters and rogues?
Fighters, rogues, barbarians, monks, artificers, sorcerers and warlocks aren’t touched, so that is half the classes there.
Rangers may get a power boost - the intention is for the new non-magical abilities to replace spellcasting.
Paladins get slightly nerfed. They get less versatility, since essentially, they lose the opportunity to use their spell slots for anything except smiting.
Wizards, Druids and Clerics get nerfed. Wizards will probably feel it the most. The Druids I’ve seen played either are Circle of the Moon and forget they can cast spells, or the other Circles and forget they can Wildshape. Either way, requiring them to use spell slots to Wildshape is unlikely to adjust their power level in practice. The Clerics I’ve seen played used their Channel Divinity very rarely, so once again, technically a nerf but not one that I believe will have a great impact.
Bards get nerfed, losing half their spell slots. This will likely impact them the most in combat, since they will have fewer spells to cast. Outside of combat, they are still the masters of the social pillar, and pretty good in the exploration pillar.
I'm sorry, what you're doing is entirely out of my experience, and I want to know how you talked your players into allowing themselves to be so weakened.
Two things: First, my players like trying new things, so they may be excited to try some of the proposed changes. Second, they can recognize that some classes are poorly balanced, so I don’t think they will object to nerfing the full casters.
One of my players expressed to me that he loved his bard character, but he felt frustrated about constantly holding back to avoid overshadowing the other characters. I think playing the new bard would be a relief to him.
These changes also enable a more low-magic campaign, and I suspect that like the OP, they may look forward to that. (This was also one of the drivers of the proposed changes: to facilitate the creation of a diverse party that wasn’t 50% spellcasters).