構いすぎか構いなさすぎで、 なんかサボテンぐったりしちゃうでしょうね とはどういう意味ですか?

質問を翻訳

構いすぎ：too much taking care of it, i.e., too much water to cactus (making its root rot)
構わなさすぎ：too much ignoring (not taking care of it, too much leaving it), i.e., too little water to cactus (making it dry out)
In either way, cactus cannot live healthy and then eventually wither or languish.