The most important feature of public elections is trust. Efficiency is one of the least important feature. When we moved away from paper voting with public oversight of counting to electronic voting we significantly deteriorated trust, we made it significantly easier for a hostile government to fake votes, all for marginal improvements in efficiency which don't actually matter. Moving to internet voting will further…
The US overwhelmingly uses paper voting (often paired with electronic tabulation). We can't "move back", it's where we are. Electronic tabulation introduces little risk when the ballots are paper.
vote by mail (and similar ballot harvesting, bulk ballot dropoffs with hazy chain-of-custody as from a nursing homes and immigrant communities) are new, based on paper, and open to abuse.
It's not where we were.
traditional absentee balloting was a small scale thing used by college students, military personnel, etc. and if it was messed up, it was not likely to change outcomes or a threat to counting accurately (no election is perfect)