To be fair, 3/5 (Zizic, Yab, Nader) you mentioned were drafted last year and all given experience in professional leagues - although they do all need quite a bit more development. Bird and Allen don't really count; in year's past, they would just be camp fodder and then cut.
Tatum is primed for some solid rotation minutes and, as has been mentioned, Theis was brought in because of his experience level - it just isn't in the NBA.
Funny enough, you didn't even mention Semi, who may technically be the 'rookie-est' of all the players you mentioned (2017 2nd round pick).