I think you're assuming evolution is smarter than it is. Telomeres make sense as an anti-cancer mechanism by making it less likely that cells replicate infinitely. The fact they also put a hard limit on age is not a problem as long as genetic carriers manage to reproduce.

"In the large majority of cancer cells, telomere length is maintained by telomerase."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4915101/