You're conflating difficulty and fun. Content required for MSQ is always going to be easy, because SE understands that a ton of players only play FFXIV for the story and are not good at or interested in improving at the game, and they want to keep MSQ accessible to those players. There are plenty of people who find that level of difficulty to be just fine and have a perfectly good time with the game. Maybe you only find enjoyment in content that gives you a challenge- unfortunately, that means most normal-level content will never be fun to you. They provide optional higher-difficulty content to meet the needs of such players instead, hence the "do harder content" suggestion. If your complaint is that overall content design is boring, rather than the fact that easy content leaves healers specifically with less to do, that's an entirely different conversation.
This game is not tailor-made to suit any one person's tastes- it is a product that is designed to appeal to as many people as possible, and the best way to do that is to keep the skill floor low in required content and provide optional harder content for players that want to go above and beyond. It's unfortunate for you that that makes you dislike the required content, but I don't foresee it changing.