chansey is literally not at all what makes rby rby. it doesn't really change the type of offense people use, because the special hits it tanks are mostly initial psychics and water/ice types, and gengar but gengar aint shit and you can wall it with plenty of stuff. electrics are walled better by ground types... basically, you can do the same job defensively without using anything extraordinary. and physical attackers are good regardless of chansey being around. chansey is good because it can tank a lot of hits and can absorb para and freeze stuff, and it beats starmie. if anything, i would say chansey is used often because starmie is very good??? if i didn't have to worry about starmie i would absolutely never use chansey because it's lame and can be a sitting duck sometimes. but what's important is you don't HAVE to use chansey to beat starmie, it's just obviously the best bet. but the fact that chansey so dominates starmie also bumps starmie down to B for me because chansey is easy as hell to slap onto a team and everyone does it (lame, lazy, foolish, etc.) and tauros and snorlax are kinda incredible regardless of what you throw at them. i think snorlax being as good as tauros is debatable (but tauros has the infamous speed and crit rate pushing it) but chansey is far from rank S and has been a lil overrated in rby in this way for like forever, and i don't get it honestly!