Is funny how opinions can differ on these - my friends and I ran through the adventures and quite enjoyed it.Well, I explained what made it a poor adventure in a different post.
As for what made it poor Tolkien fanfic:
Bilbo was portrayed as a faded has-been obsessed with recapturing his former glory-days. The adventures were rooted in a selfish desire to relive a final adventure.
In the adventures, the Shire bore no resemblance to the rustic idyll portrayed in “A long-awaited party”. Instead, the adventures doubled down on Bilbo not just being reclusive, but actively being shunned by other hobbits as a “non-conformist”. The party (all native hobbits) are questioned and regarded with suspicion when in other hobbit villages. Their relationship with Bilbo is considered a black mark against their reputation.
The Shire generally feels like a particularly unpleasant HOA.
We found it worked well at introducing us to the rule set overall, albeit only saw two races and none of the journeying aspect, but got a good feel of the mechanics in it, as it gradually introduced us to different parts of it, including combat, as we had no experience with the One Ring previously.
We also didn't find the Shire jarring, but then problem for us could be that as a group we all really like Lord of the Rings, it could be easy for us to sort of bypass the jarring bits subconsciously, and as the DM as such I may have also helped play into that - the feeling I got / evoked was more Bilbo trying to get the younger hobbits to have fun / look for adventure themselves, rather than a selfish final adventure, and the reactions people had was more around the general feel of Bilbo being different / potential bad influence on the hobbit characters (like in the books some people feared he was a bad influence on Frodo, though at same time others were thinking Bilbo would be a better influence on Frodo than the Bucklanders would have been if he stayed with them). So overall we enjoyed it, but may have unintentionally smoothed over some of the more jarring differences to the source material.