Not a bad thing!
Lower level just means the introduction levels like schooling shows and unrated shows.
So if someone says your horse would be good for lower level hunters, it means that it would probably be just fine to do schooling shows and shows that are open to everyone. But it would probably not be capable of being a competitive horse at the high levels and rated shows.
It also means that he would probably do well in unrated divisions at rated shows, so prechildres/adult hunter, or schooling hunter. I've known very nice horses who couldn't do rated level hunters but were amazing teachers and did very well at the shows.