As a Catholic very familiar with Orthodoxy, I think you have misstated the Orthodox practice with regard to marital intercourse. They do not “tell married couples what nights of the year” they can have intercourse. There are traditions concerning abstaining from intercourse on nights before great feasts, and during fast periods. However, these are traditions, not hard and fast rules. There is a very important Orthodox teaching about economia, or flexibility, in applying practices of abstaining or fasting. They are not always strictly applied.
Fasting is a requirement for all Orthodox Christians, including from marital relations in addition to meats, fish, dairy, olive oil, etc., but there is not a harsh penalty if one fails to have the self-control. Obtaining self-control is one of the purposes of the Fasts. It is something some struggle with, something their spiritual father helps them with. He can make the ruling more or less strict depending on that person’s or couple’s location on the narrow road to salvation.
Economia is needed for anyone’s true spiritual growth. It’s not about hard fast rules in Orthodoxy, it’s about spiritual progress.
From my experiences with the Catholic Church, the Catholic Church is more interested on obedience to the rule, whether that be Fasting, Birth Control, etc, than it is interested in the spiritual growth of the individual.
For example some couples, NFP is not in the best interest for the spiritual growth of the family…example, if the couple has not had any children yet, they are not learning how to truly place another’s needs above their own, something which is learned through caring for a child so by practicing NFP the couple is not growing spiritually so a spiritual father, who knows a couple intimately, will be able to make a judgement for the couple as to whether or not something is helpful or hurtful for them. Yet for some couples who’ve already had plenty of children one or more with special needs and the doctors have determined medically it could kill the wife if she conceives again and she’s already tried NFP with the assistance of the doctor and NFP councilor with the result of 4 more children, the spiritual father may determine that another method of birth control is needed, like sterilization of the husband for the good of the couple’s spiritual life and for the good of their family. The Catholic Church on the other hand, looks at their rule and whether or not the couple obeys the rule rather than looking at the spiritual good of the couple.
This mindset, I believe, comes from the Catholic Churches theology which is based soley around the idea of the Church as a Court Room rather than seeing the Church for what it is - a hospital where people come for spiritual (& physical) healing.