وَالصَّلَاةُ بِالْجَمَاعَةِ سُنَّةٌ مُؤَكَّدَةٌ لِلرِّجَالِ الْأَحْرَارِ الْقَادِرِينَ عَلَيْهَا بِلَا عُذْرٍ
The classical text describes congregation for the daily Fard prayers as Sunnah Mu'akkadah for free, capable men without a valid excuse. The commentary treats persistent deliberate abandonment without excuse as blameworthy/sinful.
A valid excuse removes the attendance demand. The detailed list of 18 excuses is taught in L025.