Do you have evidence that enemies resist shove attempts with athletics (or AC)?
That's what it says when you hover over the Athletics skill in the game. It says that it helps with both shove attempts and with resisting shove attempts. Try it in character creation. Hover over the skills.
Ah, good to know! Yes that does significantly increase the importance of strength.
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. [...]
This isn't entirely fair. Shadowheart doesn't have a lot of finesse weapon options due to her weapon proficiencies. It's not like she can use the rapier. She basically gets to choose from the dagger or the dagger. Regarding the available types of magic items, I'm just pointing out that the Str options are a lot better than the finesse options available to Shadowheart at the moment. I guess we can ask for better daggers to compete with all the other cool weapons, but shrug, I think the bigger weapons are always going to be cooler in the long run. They certainly are now, in my opinion.
True, there is only the dagger. I always forget that the shortsword is not a simple weapon! So yeah that does make a bigger difference.
I'm just pointing out that she already has a great armor class, better than everyone else. Personally, I don't think that extra +1 makes up for the loss of strength, but going with heavy armor would help someone who thought otherwise.
I think the value of a +1 to initiative is being overstated. I've played through hundreds of hours of this game, and I've seen all sorts of initiative spreads throughout multiple combats. That +1 is hardly noticeable, in my opinion.
+1 does make a big difference in 5e with it's bounded accuracy, and the benefits to initiative are hard to notice in a video game. It's not like you're looking at all the initiative scores every combat! Over hundreds of hours, that +1 initiative has probably allowed SH to go before an enemy and/or ally 5-10ish times. Which is not insignificant! Being able to cast bless or move to a different position before enemies/allies can change the course of the fight. I disagree that the +X strength/damage would be better than +1 AC, but that's more of a personal preference.
Overall, I can agree that Str would be useful for SH. But since she's a trickster cleric, I wouldn't sacrifice any of her dex for an increased strength. Basically, I think that STR is only better for characters that will use 2H weapons and/or begin at level 1 with Heavy Armor Proficiency.