In Baldur's Gate 3, I don't think it uses Dex in place of Str to determine the success of a shove. The strongest characters are the ones most likely to be able to shove a target. Being able to shove a target is a game changer on the front line of combat.
In addition to this, it directly impacts the character's jump. This is a big advantage. It helps enormously with mobility.
And on top of that, it gets the most out of the better weapons. And the better weapons... are much better, in my opinion. Shadowheart, for example, goes from using daggers to using Faithbreaker or the Shattered Flail. Because of this, she's doing more damage and better helping to control the field, especially when coupled with her spells.
Most of her ranged attacks are coming form her spells, which use her Wis, not her Dex. So not a big deal there. Certainly not in this game when it's relatively easy to long rest.
So what is she really losing? A point of AC and a point of initiative. Well, her AC is already pretty darn nice with her armor and shield. She can also eventually and theoretically take Heavy Armor and the Dex hit to her AC won't even register. The hit to her initiative is small and hardly noticeable, especially considering so many other companions have a high Dex.
As far as skills, the only ones that have any impact in this game on the front line (from the Str and Dex categories) are Athletics and Acrobatics. So the stats are one for one here, and the Str skill is actually better. Athletics affects the ability to shove and the ability to resist being shoved. Acrobatics only affects the ability to resist being shoved. Stealth and Sleight of Hand aren't particularly applicable to the front line. And for what it's worth, Stealth isn't that hard in this game no matter what your Dex is, especially since Shadowheart can give everyone a +10 with a concentration ability.
Maybe it's different in pen and paper tabletop settings. I don't know. I have done that in years, not since 3.5. But in this game, I don't think it's quite so clear that Dex beats Str when it comes to being in the front.
To clarify, I meant that acrobatics is used to "resist (grapple and shove) attempts", not "resist grapple and [make] shove attempts". Do you have evidence that enemies resist shove attempts with athletics (or AC)? Last I played BG3 it didn't tell you the exact mechanics behind determining a shove success. (I also think that Shove should be a full action, in which case SH would never shove even with 18 strength)
Bigger weapons is something I mentioned. Though if we're limiting ourselves to 1H weapons (because SH wields a shield), the difference in damage is 1d6 (dex) -> 1d8 (strength) which is not much. I wasn't considering magic items in my analysis because you can apply magical effects equally to all weapons. If Larian is only giving us cool magic strength weapons, then we could equally argue that Larian should give us more finesse magic weapons instead of giving NPCs more strength.
Jump, yes that is a big one. Though honestly, out of combat, I think that BG3 should determine jump distance based on the highest STR-party member. Handwaive it as them using the Help action to their low-STR party members. In combat though, sure without many mobility spells SH would benefit from higher STR.
Why are you dismissing sleight of hand? It's very important for picking locks and stealing from merchants if you're in to that. It seems like you're entirely focused on combat efficiency, which is a large part of the game, but not all of it.
Finally, yes SH could take the Heavy Armor Feat (at the opportunity cost of a +2 increase to her Wisdom), but all heavy armors give disadvantage on stealth checks. This doesn't really make sense for her character: a trickery domain cleric/spy. And the initiative system isn't like divinity; characters in BG3 combat are sorted purely by their initiative scores, instead of alternating ally-enemy-ally-enemy as in DOS. So any initiative bonus helps.
