When I moved to take a PhD, initially I was similarly once removed or directly involved with a number or
The world of biochemistry seemed to be one where large thoughts were generated and proofs pursued methodically over several years. There were close connections between the big discoveries and current opportunities.
It may be me but these connections are much diluted at the present. The process of developing a scientific lineage of PhD graduates from a supervisor's early work naturally splits a large field into smaller ones as graduates take an element of that work and run with it. After twenty or thirty PhDs have come out of a lab, the field has been split so often it's looking like a bastardised version of Zeno's paradox.
An example of this was a friend of mine who went to work with a scientist looking at a topoisomerase. By the time he'd arrived, two other PhD students had started and the protein's three domains had been allocated to one student each. Unfortunately, the bit he inherited turned out to be a spacer domain which let the other two domains do all the interesting stuff which made his viva interesting.
The sense of excitment I felt as a newbie undergrad scientist undertaking a short research project, the proximity to big leaps that had been made only ten years previously, waned quickly and for others too and by the mid-90s I was also mutating a wee bit of a protein to see what happened... just like four other groups around the world who were working on the same protein.