Not a lawyer, not a judge, not a member of congress, but I would suggest, as a starting point, that an "unreasonable seizure" is one conducted against a citizen who has not been convicted of a crime, as is the case with civil forfeiture. Up to the courts to decide, of course, but that's where I'd start.
I happen to agree with you, but unless we're judges our opinions don't matter.
The larger point, however, is that you can't appeal to the constitution in this case, because it's so ambiguous.
It's a huge problem and without a doubt legally ambiguous. Originalist interpretation is not a great legal framework, but it's fairly apparent some current policy is not congruent with the intention behind some of the amendments. I have no clue or power to change any of it, but it's still worth pointing out.