The reason why 1 and 2 Maccabees never made it into the finalized Jewish canon is:
(1) They glorify a dynasty with questionable credentials. The Hasmoneans (the dynasty founded by Simon Maccabee) appointed themselves both as kings and high priests of Judea. But from a traditional perspective, they don’t really have a claim towards both titles: they were not of the Davidic line (whereas the popular expectation for some time was that a descendant of King David will retake the throne - the idea that eventually morphed into a ‘messianic expectation’), and while the Maccabees were a priestly family, they were not of the traditional high priestly line, the line of Zadok.
(2) They glorify a dynasty not everybody liked. The Maccabees were folk heroes for liberating the Jews from Seleucid clutches, to the point that the names of the Maccabees and later Hasmoneans - Mattathias (= ‘Matthias’, ‘Matthew’), Judah (= ‘Judas’), Jonathan, Eleazar (= ‘Lazarus’), Simon, Salome, Mariam (= ‘Mary’) - were some of the most common Jewish names up to the time of Jesus. But they did not gain universal support. For example, it is thought that the founders of the Community at Qumran (once, and still is occasionally thought be Essenes or a related sect) were Zadokite priests who withdrew from the Temple - now controlled by the Hasmoneans - and secluded themselves into the desert. Also, there was this another group called the Hasidim or the Hasideans (the ‘Pious’) who initially supported the Maccabees, but later found them too fixated on politics and over-reliant on violence to achieve their goal and began to oppose them. Now note: the Hasideans were (one of) the predecessor groups to the Pharisees. In fact, the Pharisees continually opposed the Hasmoneans’ wars of conquest and their forced conversion of non-Jewish peoples in the areas they conquered.
Oh, and there was also the person who should have been high priest (as per tradition), the Zadokite Onias IV. Onias thought at first that the Maccabees will place him into the office of high priest when they’re done fighting with the Seleucids, but when the Maccabees failed to do so, he migrated to Egypt (the territory of the Ptolemies, the Seleucids’ rivals) with his supporters and built a rival Jewish temple there. (In fact, 2 Maccabees seems to be a work that were addressed to Egyptian Jews encouraging them to show their allegiance to the Hasmoneans instead by celebrating Hanukkah, which of course celebrated the rededication of the Jerusalem temple and the Maccabees’/Hasmoneans’ rise to power - implicitly making them reject the Zadokite/Oniad claims.)
Now the thing about 1 Maccabees - and 2 Maccabees to an extent - is that it’s a kind of propagandistic history, in a way. It tries to assert the right to rule of the Maccabees/Hasmoneans (despite their lack of necessary cred) by portraying them as the divinely-appointed saviors of Israel. In other words: since God chose them to save the Jews from gentile domination, therefore they must have this divine right to be high priest-kings - despite not being Davidids or Zadokites. Of course, those who do not agree with the Hasmoneans’ version of events would not like either work.
(3) Both works increasingly became kind of more ‘problematic’ as time went on. As most everybody here knows, the Hasmoneans were eventually replaced by the Herods and then by direct Roman rule (at least for Judaea and Samaria). Under the Herods, the work/s became a kind of liability: who would want a work that celebrates a now-defunct dynasty? (Given, Herod the Great did try to assert connections with the Hasmoneans to legitimize his rule, but he’s also the kind of person who was very paranoid about potential political rivals.)
Then, when the Romans came and proved to be not very benevolent as advertised, 1 Maccabees’ praise of the Roman Republic and the whole alliance between the Romans and Judah Maccabee became a kind of cruel joke. Really, praising an oppressor “as very strong and … well-disposed toward all who made an alliance with them, that they pledged friendship to those who came to them, and … very strong”? :shrug:
Then, after the Romans finally destroyed Jerusalem and kicked the Jews out of Palestine (AD 70-135), 1-2 Maccabees’ glorification of an armed struggle for Jewish political autonomy became an embarrassment. This was a time when Jewish survivors were disassociating themselves from the Zealots and other freedom fighters who (in their view) started the mess: it didn’t help that the Maccabees and their guerrilla tactics against the Greeks were kind of seen as encouraging zealotry.
This is pretty much the reason why the modern Hanukkah focuses on the miracle of the oil and all that instead of celebrating the success of an anti-Seleucid revolution (which was the original purpose of the holiday). The later Rabbis spiritualized, depoliticized Hanukkah to cover up any traces of its militaristic origins. 1 and 2 Maccabees were (still) a sort of embarrassment because it really kind of shows that militaristic side.