For all our travels - domestic and international - we never use any travel agency or such tour operator's trips.
We decide, study, plan n be on our own.
Our daily routines and tastes are such that we can not go with a group. We are well planned n be there a few minutes early. Not in the habit of being late or wait for someone. Strict Pure veg. Not shopholics. No drinkings. So, difficult with going in a group. We do not wish to rush. We scout for good veg restaurants n decent family hotels. We walk a lot. Let the culture sink in. We read a lot so no need of a tour guide.
For example, we spent 2 weeks in only Rome, 2 full days in the Vatican n 4 full days in Venice. 3 weeks in all.
In that time, most operators will make you tour entire Europe.