Even the post ww2 period was not all that good, more equal but nothing like a scandinavian country and the issues in the long run was worse, which is probably why scandinavian countries have performed well post 70s-80s while it is much less clear so in US and much of europe. The idea of some sort of golden age ca 1950 to early 70s seems to be a myth, since it tend to ignore huge part of population like the poor, non white and women and also don't even seems to hold true when you see videos about the society which indicate a what was called middle class was not all that well off. It may looked like a golden age vs 30s and 40s which was worse. I suspect it may simply be cold war propaganda, target against the Soviet to tell how good americans had it. In reality maybe the majority of americans had it quite bad, not maybe as bad as Soviet, but nowhere near what can be called a golden age and while things like supermarket would look rich to the Soviet equivalent, the lack of safety net indicate a poorer society than it may first look like.
US middle class seems to always been rather small, in fact the difference between past and today is not that great, there is more poor and but also more rich, which do indicate an increase in inequality, but not just one direction, but in both directions.
Also ww2 maybe gave US some advantages compared to much of the rest of the world which was damaged, however 70s did seems to expose US industry and how far it had fall behind in certain areas, lack of competition from abord may have hurt US in the long run.
Don't think Biden will fix the country, nobody in the past have fixed the country, but he could push it towards that direction that could start to reduce the major issues, but it would probably take decades of work.
UK seems to have ended up even worse post WW2, quite interesting how winning WW2 could cause major long term issues in future, but to be fair in US case the issues was always there and much more visible in 1920 and UK I don't know what happened. I suspect without WW2 they may have had performed better in the long run.
I think Biden should start with things such as scrapping the college debt, make colleges free, even if that comes at a cost of making them less accessible. Policies should focus on reducing the income gap between the poorest and the richest, the lower the better I would say since that mean stuff like healthcare should become more and more affordable and stuff like consumer goods would become more and more expensive (which may be a good things to reduce consumerism). Work conditions should be much better, like 6 week paid holiday per year, maybe reduce number of workdays to 4 and workhours to 6 and focus on employing more people rather than each person having to do more things and stop the gig economy.
If US move toward having the best work conditions, it would put alot of pressure on other countries to do the same, which may lead to a positive feedback loop. If people think this is unrealistic, keep in mind that US work conditions relative much of europe late 1880s was quite good which put pressure on european countries to improve, so now we have the opposite situation, but it can switch back. Think what difference it would have made if US decided to do that to prove how superior its system was to Soviet during the cold war instead of the red scare stuff, in fact an american worker would only need to work something like half as much as their Soviet counterpart to reach the same GDP, meaning american industries could have had 4h workdays and simply let the productivity growth improve conditions for workers overtime.