If a country can't afford to maintain it's infrastructure it's a failed country.

Very little in our world was designed to do what we need it do 50 years later. It's unlikely that anyone will even know what our needs 50 years from today will be. This is why the expectation is that systems we build will be constantly maintained, upgraded, modified, expanded, and redesigned as needed and with the next several decades in mind (to the best of our ability).

It's what we've always done with all infrastructure and even our cities themselves. Neglecting things like sewer systems until they are overwhelmed, failing, and prohibitively expensive to fix isn't inevitable. It's just bad governance. It doesn't matter if it's private companies or governments, neglecting infrastructure so that a few people can line their own pockets until the situation becomes critical should be criminal, but at the very least nobody should accept them throwing their hands up and saying it's just too expensive to fix now.