That's probably the most common mistake people make that healed in other MMOs and came over to FFXIV, myself included. I never used Benediction on WHM in most runs because I thought I had to save it for when someone is about to die. Cooldowns were often longer in other games than here, constant healing was necessary and GCD heals were bread and butter. FFXIV has a completely different approach with its focus on dps for all roles and the vast oGCD toolkit tanks and healers have to mitigate and heal incoming damage. And cooldowns like 60s are nothing. Even 120s is much less than it sounds.
It helps thinking of oGCDs as the standard way to heal and GCDs as the "oh shit" buttons to fall back on when things go south.
But it's good that you're open to suggestions and willing to look at the skills again, not often someone does it. Even if it feels strange at first, you'll get used to it with practice and you're in no rush to suddenly let oGCDs do everything. Just using them more freely and frequently with each run and watching how it affects healing is already a huge improvement.