That sounds like a “look someone managed to pull that off so it’s definitely possible” argument. In other words “you can enter the collectable creatures scene by spending that amount of effort”. And it shouldn’t be that way. The price in effort shouldn’t be that high.

Actually, it should be the customers who decide if your product is worth the effort of playing it. There are a lot of rehashed games in various genres (e.g. horrors, walking simulators) and wee see no issue with them even though they are using exactly same mechanics, or sometimes even assets. What matters is users’ reception. If users think your product is worth it - it means you spent enough effort already. If your product would be a low effort creation users wouldn’t spend money on it in the first place.

I’m sure if Cassette Beasts could accumulate that kind of playerbase and profits, Nintendo would’ve sue them too.