Is every innovation (bid‘ah) more severe and graver than every major sin (kabirah), or is there elaboration regarding this statement?

In summary: All innovation (bid'ah) is a form of misguidance, and its ranks vary from outright disbelief (kufr) to that which is merely disliked (makrooh). The extent of sin incurred by the innovator depends on whether they claim ijtihad (independent reasoning) or merely imitate others, on the impact of the innovation, and on how openly it is declared. Boycotting an innovator (hajr al-mubtadi') is a means of enjoining good and forbidding evil; it is prescribed if it achieves the desired benefit, otherwise not. As for associating with the corrupt (fussaq), it is not correct, for boycotting includes both the disobedient and the innovator. A Muslim should associate with the righteous and boycott the corrupt if there is a fear that associating with them will cause harm to one's religion or worldly affairs.