While Lucas s grab is a big commitment, he does have ways to set up into it, so it's still not too difficult to get grabs. He does get a ton of reward off it as well, and when you combine that with his great speed, mobility, pressure game, and great kill set ups (as well as extremely early killing finishers), you get a really solid character, which is definitely why most put Lucas somewhere around the top tier if not at least high. Regardless of his strengths though, I don't think he's OP. He obviously has sub par survivability, and some if his kill set ups can take some finesse to land (dair has like 0 horizontal range,grabs are more reliable when set up into instead of approaching with them).
Also, while Lucas is good in neutral, you still have a some leeway when facing him since most of his quick attacks lack range, and his projectile isn't as quick and lagless such as things like falcos lasers and mario fireballs. Overall a great character. His upthrow may be a tad too powerful, but the rest of his design fits the game perfectly