When you increase flexibility you decrease stability. Finding the right balance is key yes. But people misuse yoga. I find pilates pilates has a better success rate.
My background is 7 years in the Fitness Industry, including sports rehabilitation and including a stint as a fitness director even for carnival cruiselines as both a yoga and pilates instructor. My argument is, that yoga was more popular because people felt they could get immediate relief from tightness but they weren't actually fixing the problem.
The body tends to refer pain elsewhere. For example there's a lot of people in the world that love to stretch their hamstrings and lower back all the time. Thats a big no no.
The hamstrings and lower back are tight because they're compensating for weak glutes. But everyone with this problem hears about yoga doing wonders and they go straight to the "Pain relief" excercises. Then they eventually come to me for rehab with additional spinal problems (because all that bending forward is bad for the water in the spinal discs) and it takes 6 months longer or more to help them improve ....
Yes, we know it's all about the technique. But if your racquet collapses every time you volley..you need to add some lead to it...