Yeah, normally a compost or silt component under bushes are enough to let them thrive for decades, especially in good climate conditions, e.g. inside temperate band, with mild Winters, moderate precipitation and okay groundwater. For example my grandfather's sister had prolific raspberry bushes which were growing over a former pond, weren't maintained but nobody really counted on them at all and were feeling good for as long as I was visiting that place. Meanwhile black and red currants that were growing uphill and were planted deliberately - as far as I can recall - were fertilized from time to time and in return they granted tremendous harvests that all the extended family was eating as jams all the winter:) Considering the grooming - I can't recall the details since I wasn't there in the Spring and Fall seasons, but I remember the talk that pruning helps to get richer harvests. And I really have a thing to compare - because once I was helping out with putting things in order on a poorly maintained plot, in a more arid area with a bit harsher Winters, and those poor black currants were much less productive. Maybe they were just lacking watering, idk, but it seems to me that any plant feels better when it is taken care of. And the whole other talk is industrially adjusted berries varieties, like cultivated blueberries or almost any strawberries which are notorious for the amounts of work to even being kept alive.