UPS and FPS, Interpolating movement

Hello,
my game loop used to be
update
draw
paint
60 times per second
sleep till next frame
in case of oversleep skip frames, update more

It used to be smoother

now I have read that the proper way to do it is to lock UPS and do as much FPS as possible while interpolating movement
I decided to limit fps to 60 since there is no point to have more anyway, ( screen refresh rate, etc)

Now my game feels sluggish and unresponsibe
what can I do?