Buffy villains really do suffer from the production standards of SFX television at the time. I mean, one of the things I hate most about Picard is that this quiet "Old Man Picard" series of a retired admiral trying to deal with the ghosts of his career keeps ending on a massive interdimensional battle against entire civilizations of killer cyborgs, but it is really impressive what they can do with modern budgets.
I would say the Snake was pretty bad, but it wasn't on camera very long, and it did look sort of impressive. The other bad part were the Swordfight in Season 2, where the Stunt people show up, like it's the old Star Trek series where someone who kind of looks like William Shatner gets tagged in. But overall, the only one that really shows the limits of the budget was Season 4's foil warehouse army base.