Not sure modern greens have gone ‘too far’. Gone ‘too far’ when related to modern green speeds however, now that’s more likely.
Indeed modern greens could ‘go further’ if the desire for rapid green speeds was eliminated.
Not just a question of cost and equipment and inputs and turf health etc either.
There’s the aspect of player ability. How many players can actually handle speedy greens? Obviously there are dozens of supermen posting herein who have the touch of a surgeon over a highly polished marble floor but in reality how many players can actually handle speedy greens? Who enjoys 3-putting? And players taking more putts slows pace of play down. Put the ego away folks, it’s trueness of roll that matters.
And all this applies to entire green complexes and back up the fairway too as it’s not just what happens with a putter that’s at stake here but shots into and around the putting surface.
Atb
PS To paraphrase Basil Fawlty “Don’t mention Sitwell Park. I did once but I think I got away with it.”
First, I fully agree that people overly blame green speeds - difficult greens make the game more complex than simply length and accuracy. Americans definitely chase speeds too much - I've never heard of a stimpmeter mentioned in Scotland yet far too often I hear Americans describe a course with "These greens are at a 13!" (when in reality they're probably closer to a 10). Even with this fascination, I've seldom found a fast green in America to actually be unfair.
The issue is that people overly believe that this is all that matters in scoring, and that you should be virtually guaranteed a par if you reach the green in regulation without much thought, albeit on rare exception where you make a stupid mistake. I spent a semester in St Andrews and played with countless tourists and students - the people who enjoyed the Old the least were the ones who were overly dejected by three putts ruining their scores on what they thought should be an easy course given their GIR stats.
Contrary to popular belief, the USGA doesn't actually have any rules regarding pin placements, even though most people think a pin can't be on more than a 2% slope.
A superintendent friend of mine once said that people above a 5 handicap shouldn't be playing on greens faster than 11. This makes no sense, as short game is a much more equitable test of golf. It doesn't see age or gender, which may hinder some from being able to score with length. Therefore, it is an effective equalizer that can baffle the overconfident. Let them suffer as their ball trickles off the green when they couldn't properly strike a putt - that's a proper test!
Obviously, however, greens weren't designed to play as fast as they have. In this trend of softening greens, however, I believe most have gone too far. Hanse has done this at Winged Foot and Oakmont for the US Open, yet they were still able to host tournaments at insane speeds just fine before. And while the classic argument is that it frees up pin positions, it still dulls the test which the course presents and promulgates this idea that some pins are "illegal", when a properly struck putt would have no issue getting close to the hole.
Second, the main issue I have taken with modern greens is that they either 1) too severe for the shot being hit into them or 2) create wild double breakers that are not seen on golden age courses in America.
For the first piece, I think of many Jack Nicklaus courses. The one I've played the most is Old Corkscrew, where the 6th green features a massive plateau despite being 480 from the back tees and 420 for most mortals. It's an accomplishment simply to hit the green, and the last thing on your mind is getting on the top shelf. The same is the case on the 14th, where the dogleg green doesn't provide any angle to the fairway despite requiring a long iron approach for most players. While there are some proper outliers (such as the road hole), most American architects of the golden age held that the severity of the green should correlate to the shot being played into it. Think of Cypress Point - the 8th is incredibly severe but most have a wedge into it. On the flip side, the 16th features a fairly flat and inviting green, since from 230 it would be impossible to play for the right section of the green even for the best players.
Lastly, green designs have gone too far in creating inaccessible sections. Consider a double plateau - sure there are three sections to the green, yet they all slope from back to front, so putting from one to the other is not a complicated geometric effort. It's important to create nuanced greens with ridges and diverse slopes from hole to hole, however, I believe it's important that most greens slope to a common low point. Even on a severe double plateau, the putt is always breaking a certain way, the question is how much break to play. There are some greens, I can think of Streamsong Black or St Andrews Castle, where one may have a putt over a ridge that breaks one direction and swiftly comes down the slope in the opposite. Some of these become impossible when playing enough break will cause you to miss the ridge all together.
Long rant, and obviously a purely amateur opinion, but the question is nuanced and doesn't have a simple answer.