Benzodiazepines (Xanax, Valium, etc.) are basically that - GABAergics with very high LD50. They're positive allosteric modulators, rather than direct agonists, but the pharmacological action is similar. But benzos wouldn't be a good alcohol substitute - they're often described as less "fun" than alcohol by people who use them recreationally, they're more prone to delusions of sobriety (possibly because it's missing the other non-GABA effects of alcohol that help us gauge drunkenness), can be very addictive, and there's some link between long term benzo use and modest elevation of cancer risk, especially brain cancer.
I still found benzos "fun" but they definitely made me more sleepy and chilled out than alcohol. The disinhibition is still there which is where I suppose the "fun" comes from. The memory loss was far more extreme for me than alcohol though, which eventually made me stop taking them.
