So far blinded paths are experimental. I would not suggest 100% success when paying to a blinded path invoice.
The biggest limitation of using lnproxy as a tool to receive payments to your own node privately, was the fact that the relay would learn your node id.
If you run LND, the issue is now solved: the latest version of lnproxy supports blinded paths. Try it today.
https://github.com/lnproxy/lnproxy-relay/commit/f5670e7dc23ff95e37453a39985b80983c2b9ca6
Discussion
Nothing has 100% success on lightning 😅
But your point is very good. Adding an lnproxy shunt to your route will decrease the success rate significantly. But you just need to keep trying / play with the routing fees and it will work eventually. Plus, no custodial risk.