I will offer my typically contrarian view based on what I see "out in the wild."
IMHO, spending any money on a course ought to be with an eye to the future. Most renovations start with either infrastructure issues, i.e., "if your superintendent is fixing the irrigation more than running it, it may be time to renovate" or "if your crew is spending more time shoveling sand bunkers than raking them, it may be time to renovate, and that just to keep your course functioning so you can stay in business."
Others are driven by revenue issues, i.e., "If your tee sheets aren't as full as your comparable courses, can renovation help fill them?" And, most courses shouldn't take that mantra at face value, as when golf is down, even the best renovations might not bring in golfers, and sometimes, it's a function of market saturation more than design.
Granted, there are some classic courses with pedigree architects that have successfully become wildly popular after restorations. However, there are probably as many or more that have garnered renewed golfer interest by going the "New and Improved Tide" route. I suspect that every local market is a bit different, with the NE and all its classic courses sort of setting the standard there, but places like Texas have always had a different culture, often more rooted in modernism. Or, try to find a design that is unique in your market and/or one that will appeal to local golfers who will make up the bulk of the play/memberships.
In other words, if your course which hasn't changed its look in a long time isn't drawing members/golfers, what's to say putting it back that way is going to draw more? For some courses, looking like the course down the street might be a better design brief than looking like the course you originally were.
I will also grant that for most courses, it's hard to impose a whole new style. For one thing, older courses tend to be smaller scale, and it does take tree removal to build bigger and better modern styles, as they tend to take more room. Of course, tree removal is often a good thing as well.
Short version, follow the money, wherever that takes you.