word choice - Why does そう in 「美味しいそう」 not mean "seem" the way I think it should?

Here's another habitual mistake I make. I'm looking at a sign for a restaurant with pictures of great food. So I remark to my friend:

美味{おい}しいそう、ね？

... intending to mean, "that looks good, don't you think?" (more literally: "[that] seems delicious, huh?"). I'm going to make "good" synonymous with "delicious" for 美味{おい}しい in this question, by the way, because it's more natural for me to say food is "good".

My friend laughs, though, and tells me that by using そう in this case, I'm saying that I've heard or been informed that it is good. It does not mean that I am directly assessing the picture for myself in that moment.

Yet, when I look up in the dictionary, one of the definitions of そう is "seems" or "looks like". There's no mention of hearsay.

I've also looked at some related questions on this site, but I'm still left confused. In the answer to that question, it says "そう emphasizes evidence of the senses rather than general seeming." Well... if that's true, then shouldn't my eyes looking at the picture be the evidence of the sense I need to justify using そう?

First, what should I say if I want to say "that looks good"? 「美味{おい}しいみたい」? That seems like I am saying that the presentation might be deceptive, as in "that might be good, but that's just the way the picture is, and who knows about the real thing." 「美味{おい}しいかな」? That makes it sound like I'm seeking confirmation, as in "I wonder if that's good?" 「美味{おい}しいだろ」? That sounds to me like I'm asking the question "does that look good?"

Second, I feel like I hear Japanese around me saying 「美味{おい}しいそう」 all the time. If it involves some hearsay, then is it only used as a confirmation after someone has made a previous statement? Like so:

昨日{きのう}、めちゃうまいビーガン店{みせ}に行った！　("Yesterday I went to an insanely awesome vegan restaurant!")

美味{おい}しいそう！私{わたし}も行{い}きたい！　 ("That sounds good! I want to go too!")

Please help me kill this bad habit.

Please no technical linguistic terms. Thanks!

Answer

I believe the issue can be explained more simply than you might think. ～そうだ has two different meanings. One is, indeed, to report hearsay. The other is to make a judgement or conjecture based on a visual cue or observation.

They have an extremely similar, but slightly different formation.

For i-adjectives, if you drop the い at the end, you are using the "visual cue / observation" version of ～そうだ. If you leave the trailing い in the word, you are reporting hearsay.

When you say

美味しいそう

you are thus saying "I heard this place was good." On the other hand, if you say

美味しそう

you are saying "This place looks good."

This is especially tricky for い adjectives whose penultimate kana also ends with an "i". It's for a similar reason that I still can't break the habit of saying かわくない instead of かわいくない　「可愛くない」.