I have been using the 34C for over 26 years and have not found any upgrade yet...
My story might help:Really? No modern razor on the market today could be an upgrade to the 34C? Wow, that's quite a revelation there! So it's all hype ... Jeez! I'm sure I'm not fully understanding what you mean.
My first DE Razor "love" was a Mk1 Fatip Piccolo, which was quite a step up in efficiency/aggressiveness from the TTO Timor that I started with. (I didn't know about its "aggressive" reputation, I just got it because I liked the look of it.) After a while I got DE RAD (which many of us suffer from). I've certainly enjoyed all my experiments.
Moving up the "aggressive" scale I found that many "mild" razors didn't work for me. I purchased a RazoRock GC84 head because I liked the simple look of it so much:
Initially I found that the GC84 wasn't "cutting it" at all. Then I remembered reading that good shavers could get a great shave with "any" razor. So I decided to "train" myself to get a great shave from the milder (to me) GC84. It worked!
Gillette Techs used to be the worst for me, or great for hopeless shaves. My new favorite, again after training (or should that be retraining) is a modern (P&G Chinese made) stainless steel Gillette Tech:
I put my success down to being an SWB.