Mushrooms release water as they cook. In a crowded pan, that water collects faster than it evaporates, and the mushrooms spend their time steaming. There is nothing wrong with soft mushrooms, but it explains the missing brown edges.
Use a wide pan and a manageable amount. Pat away obvious moisture, add oil, and let the mushrooms sit against the hot surface before turning. Once they release liquid, keep cooking until it evaporates and browning becomes possible again.
If you have twice as many mushrooms, two batches are often easier than twice the heat. Very high heat can scorch the first layer while the rest remains wet. Add garlic later, when the mushrooms are nearly ready, so it does not burn during the longer cooking. Cream or stock belongs after browning if you want to keep that flavor in the finished sauce.