DC-DC Buckbooster vs M.P.P.T vs Solar Charger
This question is akin to asking "is it possible to use an engine instead of a car or an engine control unit?" - it doesn't make sense as they are components of each other, not alternatives. Your question can't get a meaningful answer.
In fact, a fairly typical solar charge controller will employ a maximum power point tracking (MPPT) algorithm to control a buck-boost DC-DC converter.