It really doesn't bother me at all for a number of reasons. Just about everyone in the crew had close connections whose absence had been eating at them for seven years. There had to be expectations of joyous reunions and after the hubbub died down returning to living the lives they were used to before having embarked on their three hour cruise.
What did Seven have to look forward to, coaxing out childhood memories with Aunt Irene? I shouldn't cavalierly dismiss the significance of her having some family and the possibility of creating a meaningful connection there. But aside from this tenuous tissue, there was the more overarching issue of whether she would be able to decide her own fate or if such disposition would inevitably wind up in the hands of Starfleet Command with consequences ranging from the merely onerous to distinctly unpleasant. I think Seven had such musings throughout the trip home, although they may have only been infrequently articulated. Despite her undeniable, if fitful, recovery of her human sensibilities and nature and concomitant bonding with others, I still feel that the options she may have perceived would be open to her were still very much an open question.
As to that long struggle to achieve a considerable degree of individuation, I think the arrival at Earth demanded that Seven be "rewarded" for her own. personal tortuous journey.
If she wasn't going to be killed off, she deserved an accomplishment that reflected the fruits of freedom and the acceptance and embrace of a consciousness so long denied.
What form would such a boon take? Advanced work on a technological marvel that would ensure winning the Daystrom Prize? Laying the template for the cure of many remaining human illnesses through the use of her nanoprobes?
No, whatever good might come to humankind through the application of her vast base of knowledge and the ability to utilize it successfully, it seems to me that the only sensible denouement to her trek would strictly be on the personal level, by means of developing and falling into an intimate romantic relationship. Developing, as in a goal to be planned and achieved, expressly finding a partner with whom she could reveal and share her growing sensuality,as well as someone who she could respect for not being intimidated by her intellect and persona.
After all, this was the culmination that Seven was being directed towards by Janeway in emphasizing the value of trust in human interactions and of course, by the Doctor in his cultivation of the ideal of the primacy of a romantic partnership. His lessons ultimately hit home, but of course, the success was a pyrrhic one. Seven would never view him in that light. So, if the object of her search would be a member of the "family", granted not an absolute necessity, but most likely seen as fitting as a crowning marker as she arrives in the bosom of humanity.
Now as to the criticisms of the relationship being an intuitive mismatch and a precipitous one at that, I think one can counter with several salient points. Obviously, there's no need to question Chakotay as having to be the object of Seven's romantic aspiration; there are no other possible candidates. But looking at the particulars that mitigate the universal distaste of the decision, you can look back to the beginning to see how the thread of interest may have begun.
I have been struck by the duality illustrated in one of the pair's first scenes together, when Seven goes off on her discourse of the ultimate failings of the human means of communication and democratic determination. On the surface, this certainly served to validate Chakotay's surety of the danger of the Borg's presence. However, both in his demeanor while receiving this rebuke and his repetition of the gist of the remarks to Janeway, I see something of a type of respect for Seven's recognition of a kind of truth in her characterization of how human interactions often play out.
Also, while I don't believe he ever states it directly, I wonder if the neural connection that was shared in Scorpion, while obviously devised to neutralize Seven as a threat, left a lasting impression of care and interest with Chakotay, though perhaps a consciously imperceptible one. I would suggest as well that his experiences in Unity naturally would make him more sensitive, even if briefly, to personally appreciate the quality of the connectedness that forged the direction of Seven's existence.
As for Seven, I think she perceived Chakotay as a man of integrity, who said what he meant to communicate without unnecessary elaboration, and had a quiet yet decisive strength (of course she wasn't privy to a lot of those increasing incidences of acquiescence that took place in the Ready Room or elsewhere out of her sight). As far as the nagging issue of chemistry is concerned, I don't believe that Seven would necessarily have an innate appreciation of its significance in a potential relationship as she approached her practice in the holo-deck with a retention of the Doctor's formulaic lesson plan. She plainly saw Chakotay as physically attractive, but the real expression of the flowering of spontaneous desire and want only reached fruition when she brooked any remaining doubts and initiated her pursuit of the relationship in the real world (my opinion). For Chakotay, I don't think I can recall any articulation of an ideation of what he would consider the qualities inherent in a potential mate, but there certainly was no sense that he didn't find Seven physically desirable and wouldn't have been anything but open to be presented with a ready made opportunity to express that ardor.
Finally as for the supposed abruptness with which the affair was presented, aside from the cues that I have mentioned, I don't know that I see many comments that attribute much significance to the quality and bond that was certainly evident in Natural Law. An experience, I think of signal importance that, granted, was near the end but was clearly not left to the final chapter.
I think a lot of the criticism, perhaps left directly unsaid, is the final disappointment of J/7 shippers who hoped for some miraculous resurrection of a dream that was long since extinguished as a realistic development. For me, the resolution as presented was certainly plausible and from the standpoint of the show runners deciding to show Seven's ultimate triumph in conventional, yet meaningful terms, was perhaps nearly inevitable.
