IMHO the issue is that lenses are too powerful. For this reason, they are liable to be used in overly clever ways that reduce readability and increase complexit

IMHO the issue is that lenses are too powerful. For this reason, they are liable to be used in overly clever ways that reduce readability and increase complexity. Things like keypaths are useful because they are (intentionally) more restricted than lenses, and are thus less likely to be misused.