This houserule makes several spells better
It's difficult to make an entire, comprehensive list of all the evocation spells that might be wrongly affected, but basically every spell that does not allow a save, or has downsides regardless of a save would be improved by your houserule.
You can make a forcecage large enough to fit several of your allies in, but the spell does not actually allow any saves. Therefore, anybody stuck in your forcecage is stuck there, Sculpt Spells or not.
Wall of [X]
There are a bunch of spells such as wall of stone, wall of wind, etc. that have negative effects that do not in any way allow saves. Sculpt Spells does nothing for these.
Everybody in the effect is deaf; no saves allowed. Every ranged attacker has disadvantage; everybody suffers from difficult terrain.
Dawn / sunburst / Other spells that make sunlight
They might automatically save to not take damage, but they're still standing in sunlight. Your drow/kobold/duergar/vampire ally is going to have a bad day.
No saves allowed; several friends might suffer disadvantages.
No saves allowed; difficult terrain for your allies as well.
No amount of automatic save success is going to allow you to see in magical darkness.
All of the spells above can currently have potential negative effects on characters in the area of effect, including allies. Your houserule would totally eliminate these downsides, making those spells significantly better.
While these are two contrary rules exceptions, and therefore ambiguous, from a story perspective, Sculpt Spell is intended to represent the evoker guiding their damaging spell to avoid the target, so it doesn't matter if they actively dodge the attack or not; it just doesn't hit them (or at least has the minimum possible effect). So I would say Sculpt Spell overrides the condition -- the paralyzed character takes no damage, because the fireball just isn't intruding into their space.
The argument could also be made that these are 'simultaneous effects' as discussed on page 77 of Xanathar's Guide to Everything, in which case the character whose turn it is -- the caster -- chooses which effect happens first, so the 'sculpt spell' effect can be the last one, overriding all previous effects.
But I think the conceptual storytelling aspect should be enough to make a decision in this case.
Best Answer
Sculpt spell protects against more than damage
Spells can have effects other than damage. Automatically making a saving throw usually means these are negated. Let's take the humble thunderwave as our example:
If Sculpt Spells had only said the creature doesn't take damage if the spell causes a save, pocketed targets would still have to make the save against being pushed.