The left in Israel is much smaller than it used to be, mainly to do with people being disillusioned with the peace process after two intifadas and endless rounds of violence, and after years and years of rightist incitement.
Recently the left wing party (Meretz-Labour combination) is polling at 10 seats out of 120 in the Knesset, and the majority Arab party Hadash-Taal is polling 5 seats, and the Islamic party Raam (not leftist on social issues but yes anti occupation) is polling 5 seats.
But the definition of left really depends what's on the table. Nobody is out right now demonstrating about the occupation or the two state solution (aside from smaller protests on the left against settler violence) because there is no proposal on the table. On the other hand, the majority of Israelis support a ceasefire deal for the return of the hostages, and the majority of Israelis did not support the judicial coup Netanyahu's government tried to enact in 2023.
In short, the left is not tiny but it's not a majority. It really needs to rebuild, and get out of the stagnation of the last years. It won't be easy. Oct 7 was a huge moment of despair for anyone who thought peace was anywhere near and it will take a lot for most Israelis to have any kind of trust in a Palestinian partner, and I'm sure vice versa. But now is the time for rebuilding and organizations like Standing Together are at the frontline of working for equality and cooperation between Palestinian and Jewish Israelis in civil society, which I believe is an essential part of undoing the racist and rightist incitement that has taken over much of Israeli society in recent years.
Editing to add: not everyone who isn't a leftist is a raging rightist. There is a big centre including plenty of people who support a two state solution in principle, but don't see it on the cards any time soon and generally think that leftists are naive.