Al salam alaykom wa rahmato Allah wa barakatohI'm an introvert, and I found out that silat arrahim is fard. Gathering with relatives is quite awkward and embarrassing for me, and I found out that hating what Allah orders us to do is kufr, so Am I a kafir like this?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

You are not a disbeliever at all, praise be to Allah; rather, you are a true Muslim. The natural dislike of some legislations is not considered disbelief, as Allah Says to the Companions (what means): {Fighting has been enjoined upon you while it is hateful to you.} [Quran 2:216]

However, you have to strive to repel this negative attitude and be keen on mixing with people in matters where it is permissible to mix with them and keep ties with your kinship to the extent of your ability. By striving to do this, you will reach what you want from this matter with the help of Allah.

Allah Knows best.