Janeway was far from 'nutty' and whatnot.
Granted, she violated the temporal prime directive, however, keep in mind that in the first time-line she bonded with the crew on a deeper level than Picard did with his for example.
They were in the DQ for 23 years together.
On most ships, crews get transfered on a regular basis after several years of service together ... but Voyager didn't have that luxury, and it affected Janeway profoundly on a psychological level.
I'm sorry, but the level of bonding Janeway had with her crew absolutely cannot be used as a justification for violating the temporal prime directive. There is now way of knowing how many lives Voyager saved that weren't saved in the new timeline she created, or how many lives were lost because Voyager was in the AQ earlier than they should have been. Hell, the orders she gave as after being promoted to admiral probably killed at least a few thousands. Also, if she really really wanted to save her entire crew why didn't she go back to the first season and send them back immediately after the caretaker grabbed them and before several others had died? Janeway is a total whackjob in my book.
You do realize that going back to the beginning itself would have profoundly affected the timeline?
Such as giving 8472 a chance to destroy every living thing in the Milky way and probably beyond?
She probably picked the last large turning point in Voyagers journey.
Also ... to go back and save Joe Carey would not have been doable ... not unless she was willing to leave the planet and it's inhabitants to continue to suffer because of radiation poisoning ... and effectively speaking it WAS the Federations probe that caused damage.
Also ... it would have been impossible for her to get the ship home earlier even if she did save Carey.
She would have to remain on-board for a while until they arrived at the TW hub anyway, because she was powerless to get the ship home on her own and needed the hub.
In-universe explanation for Janeway picking end of 7th year was probably most of the things Voyager did in the first time-line after they passed the TW hub were not galaxy-shaking events or something that would have fundamentally altered things.
Also, accusing Janeway that she caused the deaths of thousands after being earlier promoted to admiral is baloney and presumptuous because we have 0 clue from canon on what she was doing as an admiral after promotion (books not-withstanding).
The Fen-do-Mar for example.
Admiral Janeway mentioned that her favorite coffee cup took a beating after running into them, which suggests that they were hostile towards Voyager overall ... perhaps a new FC with SF sending ships in force exploring towards that region of space would go more smoothly, or sending people better suited for the job?
Who knows.
