He hasn't contributed to Yearn in over a year. Yearn is not shutting down, yearn.finance is very much still alive and has dozens of full time contributors and hundreds of part timers.

Yearn.fi, which is a UI wrapper made by Andre, is though. However, it's open source and can easily be forked and redeployed on a different domain.

A lot of these claims should be taken with a grain of salt. Bitcoin's founder famously quit one or two years in. Most of Cronje's creations will survive without him, as much as we hate to see him go.