The irony is people use sunscreen to avoid getting skin cancer, and OP is pointing out it may be causing it instead.
The benzene and sunblock ingredients aren’t just absorbing into the skin, but into the whole body. The evidence is good that they prevent skin cancer, but…
The evidence on sunblock improving all-cause mortality isn’t clear.
Here’s one study that didn’t find a mortality difference between daily and discretionary sunblock use:
You need to do the risk analysis. Until you do, you can't possibly say it's ironic using sunscreen since it could easily be doing more good than harm.