I have been following Man United since the around 1980.
The big difference here is that mid 90s we were already a titlewinning team and had our best ever generation of youngsters coming through the ranks. We didn't have massive weaknesses in our squad like we do now. Then you can do sideways moves or recruit from your own ranks. The last season with Kanchelskis and Ince we would have won the league if we just beat West Ham on the final match day, or if Cantona hadn't done his kung fu back in January. We also had enough points that season to win us the league any other year in the 90s. Point is we already had by far the best squad in the country and the class of Scholes, Becks, Butt, Giggs and Keane was ready handle the midfield the next 10 years from there. We won the PL in Erics last season here and came second the season, remember. Then we came back and won the treble with Teddy in a backup role where he played by far the least of our 4 strikers.
Right now we are as far away from being title contenders as we've been since the 80s and have much bigger issues than getting rid of Rashford....and none of the five players mentioned are better LWs than Marcus, or as good.
A new management with a better man management skills should get a chance to make this group of players pull in the same direction, work their socks off for eachother and become better proffesionals. Players with suboptimal habits and mindsets are not chronics and changing their mindsets is not as hard as you would think. You just need to address it and have the right focus on it. ETH has not found the formula and has the charisma of a brick , so it would be interesting to see a new manager have a go at it. Maybe hire some people designated to work with the mental aspect of the game and guide players who need it in the right direction, in stead of just trusting that the players either are good pros or not.
It's obvious that, right now, it's not a good environment in and around the manager and squad.