After upgrading to 7.x I realized that my RIP is not working because authentication was probably removed in 7.x. I added the routes manually, but now I am trying to choose an alternative to RIP. What is the simplest routing protocol that Mikrotik has. It should support authentication or any auth mechanism. I have 4 routers, 20 networks, nothing special. Should I use OSPF? Thank you very much.

OSPF is the obvious choice, but RIP should work too... as far as I know

RIP works in v7 just the same as in v6. If something is not working for you, post your problem in more detail, or email support with supout.rif file