Oh, there are still reasons to play Wizards and Clerics (and even Druids). First, you'll notice those spellcasters get more known spells (not a lot at first, but quite a bit more later on). As I mentioned as an option, Ritual spells could be automatically known and used maybe (at least for Wizards). I was also considering granting more uses of Channel Divinity and likewise with Druid class features.
In our group the versatility of these classes is nothing compared to the delay in time it takes when players pour over their spell lists trying to decide what to take for the day. 90% of the time, nothing changes, except maybe a few spells as Greenstone.Walker mentions, and several minutes or longer of precious game time is wasted.
Less than 1 spell per spell level over bards, and half that over clerics and druids is hardly what I would call "quite a bit."
Then 90% of the time there should be no delay. Most of the remaining 10% should also be no delay as they should know their spells and be thinking about what to switch out while watches are being taken and other things being described. The length of time it takes me to tell a DM I made changes is a few seconds on average.
Edit: I'm also not sure why you gimped Sorcerers that badly. Warlocks are a spell light class. Sorcerers aren't and you removed 1/3 of their spells.
In my two current Eberron campaigns I've turned every long-rest spellcasting class into a 'Known Spells' caster, and they all run with the same spell slot table, Spells Known, and Cantrips Known (except for isolated changes here and there-- Sorcerer gains an extra Cantrip over the others for example). And the three primary casters who normally are Prepared but now aren't (cleric, druid, wizard)... the Cleric and Land Druids get to add their domain/land spells to their Spells Known, and Wizards still have a ritual book that they use to collect any Rituals they come across in scrolls or other spellbooks (although any rituals in their book that aren't also a Known Spell for them can only be cast as a 10-minute ritual.)
Thus far there have not been any issues. And for those that are wondering about the wizard versus sorcerer thing-- in my Eberron campaigns sorcerers are only dragonmarked characters who focus on their dragonmark magic, and thus they have specialized spell lists they have to use per dragonmark and have story compels that keep them balanced against wizards.
Why do you feel this time is a waste, as opposed to "a fun part of the game."? Are the players of those wizards and clerics complaining?...several minutes or longer of precious game time is wasted.
In my two current Eberron campaigns I've turned every long-rest spellcasting class into a 'Known Spells' caster, and they all run with the same spell slot table, Spells Known, and Cantrips Known (except for isolated changes here and there-- Sorcerer gains an extra Cantrip over the others for example). And the three primary casters who normally are Prepared but now aren't (cleric, druid, wizard)... the Cleric and Land Druids get to add their domain/land spells to their Spells Known, and Wizards still have a ritual book that they use to collect any Rituals they come across in scrolls or other spellbooks (although any rituals in their book that aren't also a Known Spell for them can only be cast as a 10-minute ritual.)
At the OP
If you don't like spell prep simply playing in campaigns that ban spell prep classes is also a solution. I've played many and they run fine. No class is needed.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.