No not all of them are, there are some,
I tried to at least account for parties without a Wizard, but the deeper you go, the more you will need it. Because the identified items all tend to be the lower powered ones with the exception of the crafted ones.
That said a lot of the good weapons will need to be crafted.
I'm sorry, but I still don't understand. Can I start a campaign with a sorcerer instead of a wizard, he will also be a craftsman, and identify things from merchants? Or will there be many situations in the game where merchants are unavailable for a long time and if I want to play as a sorcerer, do I have to take a thief into the party to identify items?
Yes you can start a campaign with a Sorcerer,
No he will not have the Identify spell to Identify Items... so you will have to either buy up Identify Scrolls or pay the merchants to identify them. If you want to craft items you need to take the Academic background which will give you proficiency in Manacalon Rosery. Any character can take this background and craft magic items.
There will always be at least one merchant available for identifying items but it does cost 100 gold per identify.