Well then, that is certainly one of the endings of all time.
Do we know if the series suddenly got axed or if this was legit the ending the author wanted?
I can imagine the author having ran out of gags (surprised he kept the same joke going for over 200 chapters) and not wanting to commit to actual romance.
Like some people above said, if they wanted to end here, they could have made it a more meaningful thing of him actively going past his father's advice and doing something genuine from his own feelings. That or have his mom give him advice for once and have it be actually useful.
I also like the idea of them getting together earlier in the series and have the advice switch from "how to become popular (with women)" to "how to navigate a relationship" but I get that a core comedic beat of the series is Evans trying to woo every single woman he comes across, not to mention that it's already kinda awkward when Kurt is messing around with other women when he is married, so having Evans do the same when we care more about Oakley would not really fly.