Mokujin beats down any single bijuu, or catches a TBB and throws it back at the bijuu that fired it. If multiple bijuu fire TBB at once, that gives Hashirama an opening to use
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to restrain them and then slam down deity gates on them, or elevate the ground below them with mokuton to redirect the TBB like Kitsuchi did, or pummel them with mokujin, or suck them dry of chakra with wood dragons, or put them to sleep with flower tree world...Hashirama has lots of options here and his jutsu are well-suited to fighting bijuu.
Obito himself gets killed by Hashirama.
-SM sensing means Hashirama knows exactly when Obito becomes tangible and will know his location the moment he reappears after warping
-Wood clones gang bang him and attack as he becomes tangible to warp one clone
-Healing and SM durability means almost none of Obito's physical attacks are gonna work, he has kamui and black rods, and that's it.