To an extent, bikes are proportioned in length and seat tube height. It's not always true, and there's no fixed formula, but while seat height can be fixed with a longer post, overall length is harder to correct.

There's also the question, as in your case of handlebar height range. Modern bikes use more sloping top tubes so bar height vs saddle height is easier to fix, but on older horizontal top tube bikes you run into the issue you're having.

If the bike is long enough for you, then some sort of stem riser or adapter may solve your problem. Or you can look for a relatively modern frame similar enough to yours to switch over the components, preferably one with a sloping top tube. Frame replacement is the best bet if you can do it yourself or have a bike co-op nearby, otherwise the work can be costly.

I don't think going back to an older bike is going to make you happy. Bikes have improved considerably over the years, and you'd lose too many of those improvements.

One other option might be to find a modern used bike that meets your needs, and sell yours. If you shop hard and sell smart, the spread shouldn't be more than you might spend trying to rework what you have.

I hope I gave you something to think about, the rest is up to you.