First, marriage is both a civil/legal institution and it is a sacrament.
The Church simply cannot separate the two. Marriage is not like baptism where the Church can say “this is our ceremony that we celebrate and it has nothing to do with the state.”
Second, if your concern is financial, that’s perfectly reasonable.
This is what you wrote
We are both in out late 60’s and have friends that have experienced financial losses because of spouses medical bills.
It is possible to make legal arrangements to specify how financial obligations are met; in other words a pre-nuptial agreement.
Now, someone surely is going to say “Catholics cannot have pre-nuptial agreements.” That’s simply not true. They happen all the time.
What is true is that Catholics cannot enter marriage while making an agreement that says “if this marriage ends in divorce then…” That kind of agreement/contract is contrary to the permanence of marriage. (There are some others, but suffice to say that’s the biggest problem).
There are civil lawyers and canonists who can help couples prepare pre-nuptial agreements that do not violate the Church’s teaching on the permanence of marriage.
I would suggest you talk to your pastor about working with those lawyers and see if what you would like to happen (maybe an agreement about keeping separate finances) can be put into place.