I found this line a bit amusing. I completely agree, Sentinels and night elf military in general were in no way designed to siege cities. There really weren’t any walled cities on their entire continent (besides Dire Maul, maybe) to practice on, and no hints of a desire to expand their territory into their neighbors to require siege equipment.
Of course, this then led me to the thought… why would the blood elves have siege equipment? They also seemed like an isolationist culture, and the only enemy they’ve been fighting for a while are the forest-based and guerilla-fighting Amani - who I suppose have a single city, but it doesn’t seem like siege warfare would be something the blood elves would have had regular practice with. Unless, of course, they were running training exercises just on the off-chance they had to go to war with those humans building large cities near-ish to their border…
That’s probably not at all what Blizzard intended with those lines, but I find it fun to conjecture anyway. 
I agree - I think there are some people who’d still grumble, but I think the complaints really spiked when it was learned that one of the first joint Horde actions was… genociding the night elves.
What I expected from the nightbourne going Horde: “You know, thanks for the save and all, but I think I’ll go drink some mana crystal martinis with my blood elf besties instead of going on your no-magic nature yoga retreat. I’ll send you a postcard. Maybe.”
What Blizzard gave me on the nightbourne going Horde: “You didn’t smile and give me a lolly as you saved my life, so I stood by and let/helped my new friends burn your family to death.”
Just… I didn’t expect hugs, but Thalyssra at least needed to have an immediate reaction to Teldrassil and some sort of comment on her previous teamwork with the night elves.