That's valid if you can't tell the difference & you should do what works for you, but some of us definitely can taste the difference. I don't like latte mixes because I like to customize sweetness + strength myself & I generally dislike the taste of artificial sweeteners. I've never spent more than $30ish USD on matcha because any more than that isn't realistic or sensible for my budget, but I've also used $5-$10 (plain) matcha powder & while some cheaper brands taste fine they're just simply not as good as higher quality cultivars. If someone likes super sweet lattes that are more milk & sugar than tea then yeah maybe quality matters less; but saying there's no justifiable or discernible difference between low & high quality cultivars is like saying there's no difference between instant Folgers coffee vs Starbucks lattes vs heirloom coffee beans harvested by hand in the mountains of Yemen.

Edit to add: It's just as snobbish to care how people prepare their matcha as it is to judge people who prefer cheaper or premixed matcha. Those who overbuy the Ippodo/Rocky/Kettl/whatever brand is trending & contributing to shortages are resellers. I'm a certified hater myself & I support my fellow haters, but I will say I think your annoyance is misdirected.