Faith in God moved the Israelites to obey by going and looking upon a brass serpent. Yet no one today can be saved by going and looking upon a brass serpent. Faith in God in the NT requires one repent Lk 13:3 confess Mt 10:32-22 be baptized Mk 16:16.
Only believing.
The Israelites did not have to look and then baptize. They just had to look.
John 3:14-18 And as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up, that whoever believes in him may have eternal life. “For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life. For God did not send his Son into the world to condemn the world, but in order that the world might be saved through him. Whoever believes in him is not condemned, but whoever does not believe is condemned already, because he has not believed in the name of the only Son of God.
John 5:24 Truly, truly, I say to you, whoever hears my word and believes him who sent me has eternal life. He does not come into judgment, but has passed from death to life.
John 6:40 For this is the will of my Father, that everyone who looks on the Son and believes in him should have eternal life, and I will raise him up on the last day.”
John 11:25-26 Jesus said to her, “I am the resurrection and the life. Whoever believes in me, though he die, yet shall he live, and everyone who lives and believes in me shall never die. Do you believe this?”
As far as Mark 16, there is dispute about whether that was part of the original manuscript so basing doctrine on it is not a wise course of action.
That passage also goes on to say that those who believe And these signs will accompany those who believe: "in my name they will cast out demons; they will speak in new tongues; they will pick up serpents with their hands; and if they drink any deadly poison, it will not hurt them; they will lay their hands on the sick, and they will recover."
If you are going to demand accepting baptism as part of salvation,t hen the rest of this MUST follow. Do you also advocate all of that? Do you speak in tongues, cast out demons, lay hands on people and see them recover, drink poison, or snake handle?