The available sources contain information only about the acute effects of alcohol on memory formation, not about long-term effects. The evidence needed to answer this question is therefore entirely absent from the supplied literature. The honest answer here is: unknown on the basis of these sources.
The available research sources contain only one partially relevant article1, which concerns the acute effects of alcohol on the brain. That article describes how alcohol temporarily disrupts the hippocampal system, the brain region responsible for forming new memories. This explains why people can experience memory blackouts after heavy drinking: the formation of new memories temporarily shuts down.
The provided sources contain no information about the long-term effects of alcohol on the brain, such as structural brain damage, dementia, cognitive decline, or changes in brain function after years of use. On the basis of these sources alone, it is therefore not possible to give a responsible answer to the question of what alcohol does to the brain in the long term.
For a complete picture of the long-term effects, you would need sources on chronic alcohol use and brain atrophy, cognitive decline, or alcohol and dementia risk. That information is not present in the current research base.
Only one abstract available (PMID 20049223), covering acute alcohol intoxication and memory formation exclusively. No sources on the long-term effects of alcohol on the brain are present.