About 20 years ago I engineered a classical music CD for a major label. The original analog tape recording, featuring a famous orchestra and conductor from the 1950s, had been made with a considerable degree of compression. (Compression is related to AGC although the dynamic behavior over time is somewhat different.) As the analog tape was being transferred to digital I sat with my hand on a gain slider, raising and lowering the gain along with the music for the entire length of the recording.
The CD got positive reviews, and to my knowledge, no one outside the record company was ever aware that this kind of thing was done. Just don't try to go too far--as I recall I only made about 6 or 8 dB total change in the dynamic range. I would never claim that the result sounds exactly as it would have sounded without the compression, but it generally sounds better and, I hope, in no way sounds any worse than before.
Where people get into the most trouble when trying to "fix" a problem recording is that they overuse whatever tool they're trying to apply. It's very important not to do that, since then the attempt at a fix can become just one more audible layer of the problem.
--best regards