While I agree a more serious romantic rival might have been more intriguing when pursuing Jill, Tybalt's buffoonish character is absolutely necessary for helping maintain the overall light atmosphere of the game, and in my opinion his presentation is the most laugh-out-loud entertaining moment of it:
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Tybalt's presence is not just for a false or inadequate competition for Jill, either. He's set up as a contrast for Sage, who is a complete opposite despite their upbringing by mutual parents.
Additionally, he could also factor in why Bella has issues with Jade. We do not yet know what those issues are exactly, but parents are often judged by their children, and she completely loathes Jade's son and had a false impression of her daughter.
So, the Tybalt character has other uses other than trying to cock block you.