I do not find Sasha’s skating brittle or fragile at all. I love to watch her because I find her skating to be extremely powerful and muscular. It takes incredible strength and balance to achieve her positions on the ice. It is one thing to be flexible enough to do Biellman positions, but it takes more strength to extend the free leg without assisting with the hands. I think Sasha has the best spins and spirals and footwork of any female skater because of the strength she has to achieve amazing positions.
One reason she is criticized for being fragile is that she is heavily influenced by ballet, and her movements are light and controlled like a ballet dancer. Many people find ballet dancers to be fragile because of their lithe bodies and airy movement, but dancers are extremely strong. In fact, although Sasha is praised in the skating world for her balletic quality, I doubt she could make it as a professional dancer because most dancers are capable of achieving even more difficult positions than Sasha.
Another reason her skating is described as brittle is because of her poor jump technique and her wobbly landings. Some people are not able to enjoy performances without solid jumps, and Sasha is lacking in that area compared to her competitors, but her triples are decent enough that she can compete with great jumpers. Thankfully, she is not as deficient at jumping as Lucinda Ruh, so Sasha has been able to rise through the ranks by compensating for weak triples with superb quality on her other elements.