I like the old Stanleys. When I got into woodworking, I picked up some older ones, gave them a good once over, and have been happily using them since. Mine are mostly from before WWII. They were cheap, well made, and work really well.
I have old #2, #4, #5(early bedrock), and a corrugated #7 Stanleys. I also have a 78 rabbet plane, a 40 scrub plane, and a couple of old Stanley spokeshaves (one flat, one curved sole). The one newer Stanley plane I have is a 220 block plane from the 1990's. I'm really impressed with it as well. I can't say it works any better than the Veritas low angle block plane that I also use.
For the bench and block planes, it's really hard to beat the value of using an old Stanley or a Record.
My theory is that, after motorized hand tools became affordable, the hand tool market shrank quickly and it was a race to the bottom for the plane manufacturers. Engineering and development of the hand tools all but stopped. They competed mostly for low price, not best function. Eliminating shop class from most schools didn't help the long term market.
When I clean up an old plane, I do like to replace the chip breaker and the cutter with thicker replacements - reduces the chatter. Even without that, they still work well.
For the "specialty" planes, which are harder to find and more expensive, I've found the modern replacements are easier to get and sometimes less expensive. For instance, one of my favorite planes is a bevel up low angle smoother. The modern Veritas version is cheaper and works better than an original Stanley (if I could even find one). Same with my medium shoulder plane and scraper plane.
One thing I've decided for myself, after a little effort and experimentation, is that cheap new planes are NOT worth it for me. I tried to get a Kunz working well, also an Anant. I found them poorly machined with flimsy castings and cheap plastic parts. Even after quite a bit of work, both were prone to chattering and would not hold their adjustments well. A friend asked me to tune up a Buck plane (from the big box store). The casting was some sort of very soft metal that looked like iron (but wasn't). I gave up on it and cleaned up a $10 old Stanley for him that now works just great.
I do love using a nice sharp hand plane.