Accurate measurement of anything takes one closer to reality. In the realms of fat loss, a negative energy balance is the sole means by which fat loss occurs. Therefore it makes sense to categorically know that this energy balance is being achieved.
To eyeball food and estimate calories is only applicable to those trained in calorie counting. To those with vast experience and understanding of calorie density within the foods they eat. If enough knowledge is attained, it can become automatic. But only then.
But to the untrained individual seeking fat loss, it is short sighted to forego the rigorous tracking of their calorie intake. Furthermore, refusing to measure accurate quantities of food disarms one’s ability to realise accurate quantities of food. The accuracy of one’s energy balance is therefore compromised.
If fat loss is the goal, unweighed heaped spoonfuls, handfuls and multiple knives of food can be consumed if desired. But it’s probably a good idea to be aware of the compromise (or non compromise) this has on the overall calorie target over time. That way one can adjust and stay on track.