Who knows what there is in other people's heart to assert that they have spiritual pride?
My opinion is entirely the opposite. A rule is a generic commandment that applies to the whole the community. The common rule says that fasting is one meal after 3 PM, period. If it were particularly strict and out of reach, it would not have been enforced on everybody. Consequently, the one who follows is not individualistic but simply follows the rule that was taylored for the full community. An approach is individualistic if it departs from the common rules defined for everybody.
If the strict rule used to be commonly followed (which I do not know because I do not have testimonies of past centuries let us say from 4th century to nowadays, so it is an assumption), and that nowadays nobody knows it or follows it, it questions the faith of, we, people of nowadays, or our laziness, or maybe our pride because we think we can depart from the rules without explicit blessing and without confessing it. In theory, the fact of not fasting properly should be said in confession, not the fact of fasting properly. Would someone from the past centuries have needed an explicit permission to fast according to the rules? I doubt so. So, why should someone from our time ask for such permission? Is it the one who follow the rule that needs guidance or the one who does not follow it, so that he can find at long term the way to follow them, even if temporarily, they are alleviated for him? We should not twist the things so that the one who follows the right tradition is now accused.
If everybody willing to come back to the pious customs is suffering spiritual pride, then the kollyvades were spiritually proud because they rejected the deficiencies in the practice of their time sticking to the rule rather than the decadent practice of the moment. Other examples. If I am lady and that in my church nobody wears the veil because nobody knows the rule, am I going to be accused of pride because I wear one, because I simply follow the rule? The same if I stand whereas most people sit? Moreover, if the fast is secret and that I do not feel superior to those who cannot do it i.e he does not judge them, there is no pride. Not following an error that became collective by mistake in order to stick to the rule is praiseworthy and not a symptom of pride. It is to be done even if those who are in error are a majority and scandalized.
That if one keeps the Divine commandments are others are scandalized, one should disregard their sense of scandal
Yes, I know that there is a kind of scandal that one should disregard. And what is this? Listen. When you perform one of God's commandment or observe the Divine and sacred canons of the Holy Apostles, or of the Ecumenical and local synods, or the Traditions of the Church, and, quite simply, when you strive to do the will of God, and another person is scandalized on this account, then you should disregard the "scandal" and carry out the commandment of God and observe the Divine and sacred canons, saying to those who are scandalized and would hinder you what the Apostles said to the Jews : "We ought to obey God rather than men"
From Christian morality, by Saint Nicodemos the Hagiorite Discourse X page 392-393
The problem I see on this topic is mostly ignorance. Most orthodox (even True orthodox) do not know the rule of one meal after 3 PM because they were never told; I was myself taught this by a non-orthodox! There is an utter silence on the topic, even from pastors Consequently, a part of the ascetical dimension of fasting is lost and ignored : someone who already fasts from meat and so on, will simply miss the next step (one meal after 3 PM rule) because nobody ever told him. Since fasting is closely linked to the spiritual life, it is hindering spiritual progress: it prevents to wonder oneself what one can add or change to his spiritual life in order to be able to meet the standards, it prevents from using the full weaponry of fasting against passions. Human nature has not changed, so the medicine to cure it from passions are the same.If the man from 6th century required fasting until 3 PM to curb passions and all, I do not see why the man from 21st century would not. Unless human nature changed meanwhile. I am afraid the only change that occured has been an increase in laziness leading to regard laziness as the Tradition per se, which is totally non sense.
If the rule was known, the benefits would be many : people would try to follow it, would make intensified spiritual efforts. Of course, not everybody would reach it, or not immediately but, but this, per se, is not a problem; spiritual progress is a constant journey in which you have always to progress, even for those eating dry bread and water once a day of course.