I use Cokin & HiTech slot in filters .
A size fir TLRs and range finders , P size for SLRs , DSLRs , mirrorless and some medium format , and the Z-pro size for some medium format and large format .
ND grads , NDs , polarisers , Infrared pass filters , B&W filters , and a few colour correction filters for colour film .
They still have their place , and will continue to be used .
I occasionally use the close up filters , but all the cheesy 80's ones I'd been given and not used are long gone .