Do you mean those ‘affordable’ modern phono preamplifiers that cost $1000 or more, contain about $50 worth of parts if you’re lucky and sound ordinary? Not a lot.
You first need to understand that I’ve been spoiled by great phono preamps made when vinyl was at its peak. Much of the excellent equipment from that era is unsurpassed in terms of build, technical specifications and sonic performance. Cheaper, modern gear simply cannot hold a candle to it, despite all the hype and often impressive on-paper specs.
There isn’t a lot new in terms of analog circuit design and engineering that improves phono preamps. There are improvements in opamp design and miniaturisation though and these things save money. The very high cost of labour and the resulting increased production cost of gear these days mean that reducing construction costs is critically important.
These days we have affordable phono preamplifiers filled mostly with op-amps and cheap, miniature passive parts. Very few affordable discrete designs containing really high-quality parts exist.