A.T PhoneHome: In the ending position, Spassky's pieces are all protected.
Black threatens ...Be3. Like <30.Qc5 Be3 31.Nxe3 Qf7>. Now 32.Nf5?? would allow mate; <32...Nf2+ 33.Rxf2 Qxf2> and <...Qf3#> mate. If <32.Nxg4>, then <32...Qf3+> wins <(33.Kg1 Rxg4#)>.
Another variation is perhaps <30.Qc5 Be3 31.-Queen moves-> and now Black has <31...Nf2+> (if c2 Rook captures, 32.Rxf2, then simply 32...Bxf2 and Rook is lost).
So King has to move, <32.Kg1> and Black has <32...Rxg2+> (checkmate if 33.Kxg2??). Now <33.Kf1> would be self-destructive as <33...Rg1+> means King has to play <34.Ke2> which loses a1 Rook; White has lost both Rooks!
May not be the most correct variations I just gave; probably better moves for White there but I think you 1) get checkmated as White or 2) lose a lot of material preventing speedy mate.
White's Rooks and Knight are stuck passively in the queenside while Black has each piece protected by another piece PLUS they are all on the kingside and in my opinion he can play many tempo-winning moves, forcing White to reply.
My take on this pretty chess game!