Offline mode has been replaced by local accounts, which still allows you to play Minecraft offline but does not allow you to download Minecraft. In order to download Minecraft, you will have to sign in to the launcher using a online account (Microsoft/Mojang account with Minecraft purchased)
PojavLauncher does NOT, and will NEVER support piracy acts. You MUST purchase Minecraft legally and follow Mojang's Terms of Service to download Minecraft. To purchase Minecraft click this.