Don't get stuck on labels.
Alchemy means much more than a search for physical gold, which Newton certainly did work for. Remember As Above (physical), So below (spiritual)...
Indeed Newton saw himself as a spiritual alchemist believed that alchemical knowledge was related originally by 'supernatural' entities. One can deny ancient as being backward, but none of these alchemists were and what was then, still is now.
As for theories, modern or not, Arty, some stuff cannot be backed up yet it sill Is...
"Hence scientists avoid commenting, but pretenders and quacks may go where professionals fear to tread. "
Pretenders and quacks?
Indeed, you are right that some do dare to go where old paradigm 'professionals' fear to tread.
Thank goodness for the maverick scientists...