I recall Amazon’s Lord of the Rings title sequence [1] received some criticism for looking fake, even though they filmed it practically [2]. I’d guess it was due to folks assuming title sequences are CGI, combined with the fact that few people really know what poured liquid metal is supposed to look like.
There's a similar problem with gunshots and explosions - we want what movies have given us which is not what they actually act/sound like - so much so that live recordings of actual gunfire/explosions is often deemed "fake".
Bad practical effects do exist, but even when bad they don’t look “unnatural”.