To be fair, the most well known examples of architecture tend to cost a lot of money to construct, and people spending lots of money want someone with experience. If you look at painters for example, a lot of them produce great work at relatively younger ages than architects, probably because the barriers to entry are lower.
Still, it seems that in the arts, you can continue to produce great work for a long time. For example, Frank Lloyd Wright was around 67 years old when Falling Water was built and Leonardo Da Vinci was over 50 when he painted the Mona Lisa.
> Frank Lloyd Wright was around 67 years old when Falling Water was built
As a teenager in rural Wisconsin, Frank Lloyd Wright worked for a graduate of MIT school of architecture and then went to Madison to work for a civil engineering professor at UW Madison. His big break was to run away from home and go to Chicago, which was in the midst of the largest building boom in the history of the world up to then, where he was hired within a day of arriving by the firm owned by the MIT grad he worked for years before.
The guy started very early and then never stopped working.
Still, it seems that in the arts, you can continue to produce great work for a long time. For example, Frank Lloyd Wright was around 67 years old when Falling Water was built and Leonardo Da Vinci was over 50 when he painted the Mona Lisa.