Except you would never get republicans falling off, or rather those numbers are extremely small. So now you get a situation where a large part of your voterbase goes "ewwww" when you tall about "the Wall". And you lose votes from progressives. Remember - Trump got the same amount of votes he did in 2016. Dems lost like 6 milion of them.

You don't "step back towards the left" by promising right wing policies. Especially comming off of a 4 year period of a democrat being the president. You don't talk about your opponent "having good ideas".

A correct move to the left would involve a "Biden is Biden, that old grandpa, he does stuff that I, the hip new gal in town will change!". It would involve an immediate hard stance on Gaza. It would involve a shitload of other leftwing policies. Instead you got the "status quo" as you put it which obviously sucks and people don't like it. You can promise anything you want during the lead up to the election. Don't promise republican shit though because why would people vote for a "republican with no sugar".