Hi, I think what you are seeing is that demand has shrunk for HiFi systems. I remember while growing, my Dad had a very nice Pioneer system that sounds a lot like your old system. He bought it while he was working his way through college in the early 70's as the night shift manager at a Holiday Inn, so I'm sure he didn't pay the price of a new car for it. Most all of my friends houses in the 80's had a similarly competent stereo systems in the living rooms.

Now, most middle-class households have a soundbar and a couple Bluetooth speakers that don't sound half as good as the stereos people were listening to 30 years ago. It seems like main stream society has kind of stopped caring so much about good sound, so what is left of the industry is proportionately weighted more toward the high end enthusiasts who are easy prey for snake-oil salesmen with marketing propaganda.

The fundamental task of taking a small sine wave, making into a bigger version of itself and using it to create a pressure wave by using an electromagnet to move a cone has only been slightly refined in the last 100 years. There really are no ground-breaking technologies or exotic materials needed. There is no functional reason to spend tens of thousands of dollars to do this.

The two biggest changes in the last few decades have been that for whatever reason, mid-range manufactures have moved away from making large full range floor speakers with 12 or 15 inch woofers toward main speakers with smaller drivers and a separate powered subwoofer. The other Big change is digital sources and streaming services.
If your Sony stuff you have is what I think it is (I have Sony SS-cs5 bookshelf speakers in my secondary system) it is really quite sufficient. All you are missing is a powered subwoofer, and a DAC. I would start with getting those items before replacing the Sony stuff, which you may be perfectly happy with.

Unless you're a bass-head, you'd probably be more that happy with an entry-level 10 or 12 inch Sub for $400-700 from a subwoofer specialist company like SVS, Rythmic, RSL or Outlaw Audio. If you want to connect your smart TV, computer or Cell phone to your system, you may want to get a DAC, Digital to analog conversion really isn't The rocket science the manufactures make it out to be. Spending more than a few hundred dollars on something like a Schiit modi, or a Cambridge DacMagic would only bring minor but very expensive improvements so small that human ears can't hear the difference, but your dog might appreciate. I have done a lot of blind A/B testing and I know my ears are too old to hear the difference and I'm 40.