I did dislike it fairly. With how much he'd constantly abandoned his family and practically ignored contact with his friends for years in order to train, this felt like a final straw. It's even more insulting in the anime where it adds additional scenes to show Goku's skill at being a caring grandfather.
Despite that, however, I wouldn't say it's bad writing when giving it more consideration. Much like with Ging's decision to leave his family to explore the world in Hunter X Hunter, Goku's choice comes more from the difference that some Asian Buddhist teachings have compared to Western values as in both cases, the characters are leaving their personal attachments behind to dedicate themselves to a larger cause. Whilst Goku's goals in training Oob did have the selfish aspect of wanting to fight a strong opponent, he did make it apparent he also wanted to train Oob as a successor in defending the Earth. It would also be seen as a waste if such a prodigy wasn't taught how to draw out his full potential and passing the responsibility onto another character wouldn't have been enough. For what it's worth, Neko Majin Z suggests that in Toriyama's mind, Goku still visited home now and again unlike in GT, so training Oob may have been closer to the idea of someone moving for work and returning home when they can. Separating Oob from his family would be more unfair as well, considering he was still a child.
So overall, Goku's decision is one I personally don't like, but one I find nothing objectively wrong with in terms of a writing decision.