What is the ruling on delaying one's congregational prayer until it has finished, then praying with someone else in the mosque, and what is the ruling on someone who delays by distracting himself or procrastinating, then finds no one to pray with, so he prays alone?

Allah records the reward of congregational prayer for whoever misses it due to a valid excuse, according to the hadith of Abu Hurairah: "Whoever performs ablution well, then goes out intentionally to the mosque and finds that the people have already prayed, Allah will record for him a reward similar to that of those who attended it, and that will not diminish anything from their rewards."

There is no blame on someone who has food served to him to eat, even if he misses the congregational prayer.

One who misses the congregational prayer at the mosque should be keen to pray it in congregation with another person, or look for another mosque. As for laziness without an excuse, it causes one to miss a great reward and may be sinful, due to the difference of opinion among jurists regarding the ruling on congregational prayer in the mosque, whether it is obligatory or recommended.