Better frigates get flux locked, die to fighters, and don't have 8 small ballistics. Watch an IPDAI one snipe salamanders and harpoons with its light mortars and you'll understand.
It's not a wolfpack frigate with a medium energy mount and stacked 20% damage bonuses; it will never be an opportunistic close-quarters cruiser and capital killer. Ballistic weapons (aside from meme point defense builds) dominate mid to long range. For 6 DP you're clearing a zone of fighters and missiles while killing most frigates, bullying destroyers, and occasionally swarming a solo cruiser.
Field Repairs covers basic battle damage and 35% of recovery costs. Think of the Vanguard as most of the point defense of an Omen, the frigate killing and destroyer pressure of a Tempest, and the peak performance time of a mid-game SO frigate. For 6 DP and an occasional 20 supply repair cost.
If you've been exploiting the wolfpack meta with close-range energy builds, yeah, the Vanguard is terrible at that.