I don't think Ardent Censer is fine. It gives a decent amount of AP to start with which is great for most shielding supports. Next it gives movement speed, also another great thing for AP supports and CDR. It also Than it gives the increased healing and shielding so yeah it's already above average compared to other forbidden idol items if you ask me when it just comes to base stats.
Than you also have the easiest applicable passive compared to the other support items that buffs A/S and gives free healing. It also gives on-hit damage to whoever you shield and lasts long enough that you can usually have it up 100% of the time. While redemption and locket are used situational (only in teamfights and you want to make sure good position and blocking damage), Ardent Censer is always good.