There’s been some debate as to when Whirlpool started to decline, but I’d argue the decline began once they went to the direct drives. The direct drives have (and still have) issues with the transmission and slipping into spin when it’s cold or the neutral drain pack fails, the belt drives could never slip into spin because of the design.
Belt drives could have issues with the transmission, but was seldom compared to the direct drives.
The biggest gripe about the direct drives is the rinsing performance since they don’t do multiple spray rinses on the first spin to rinse away the soapy water and detergent. Another thing that affects the rinsing performance as well on the direct drives is the pump runs in either direction vs the belt drives which have it only run on a single direction. My hypothesis is on the direct drives is the soapy water that’s left in the drain hose gets pumped back into the tub when it begins the agitation for rinse. Since the pump aerates, it can kick up some suds in the rinse.
The belt drives on the other hand only have a pump running in a singular direction, since there’s multiple spray rinses on the first spin, it essentially pushes away the soapy water away as much as possible. There will be some of the soapy water in the pump, drain hose that will make it’s way back into the tub but will be pumped away for a second or so before the transmission engages for the rinse agitation. Since there’s even more spray rinses on the final spin, it pushes away even more of the soapy water (what little there is left in the rinse) away. Just an observation I’ve made over the years.