The reason the first one is grandma-ish is for a few reasons
1. It's baggy. The shirt is ok to itself but not with the skirt because they are both baggy In my opinion you need a combination.
like a maxi skirt with a sort of bulky jacket, like a jean jacket.
2. The Print overly dramatic prints such as small floral prints give you a more grandma-ish look. below are some examples, just note as pretty as some of these fabrics are they just don't belong on clothes.
1. Fits nicely not too tight but not baggy or frumpy. The cut of the clothes is very important.
2. Simple Patterns, Bright Colors, Not that bright colors are necessary but I think it's better with atleast one. It's good that the color is bold not patterned, but colors in patterns can be good if it matches the shirt. Usually simpler is better. Here are some examples of good fabrics