A single individual cannot be expected to carry out all the 613 mitzvot in the Torah.
For example, there are mitzvot that concern only a man or a woman, a priest or a king.
But a person can perform them as part of the whole of Israel, as an integral component of a particular generation in time and place.
Every generation is a cross section of the timeless entity that is Israel.
Even if a person cannot carry out a mitzvah in terms of action, he can perform it in speech and in thought.
By reading aloud and studying the Torah, all 613 mitzvot find their expression in the individual’s soul.
There are many levels of uniting with the Torah, depending on one’s capacities.
There are those who are limited by their intellects.
Others are limited by their willpower or their soul roots.
A person may comprehend something in Scripture and yet be unable to make contact with it because the root of his soul shrinks from it.
All people are conscious of an attraction to certain aspects of the Torah and an incapacity to react to others.
–Rabbi Adin Steinsaltz
From Pebbles of Wisdom from Rabbi Adin Steinsaltz