What if I cannot do the poses everyone else can do?
Then you practise the version that belongs to your body. Yoga is not synchronised gymnastics. Bone structure, proportions, mobility, strength, injury history and experience differ, so two sincere practitioners may never look identical in the same asana.
Use props. Bend the knees. Reduce the range. Rest. A modification is not evidence that you are failing; it is often evidence that you are paying attention.
The deeper practice is to notice the mind that immediately compares, judges and says “I should be able to do that.” That mind is also part of what yoga invites us to observe.