Madrid must be in financial problems though based on their net spend. If they don't sign anyone else this window it'll be the 4th season in a row they haven't spent more than 100m euros.
In the last 5 seasons they've:
Bought: €363,750,000
Sold: €321,550,000
Net Spend: €42,200,000
That's not normal Real Madrid.
They got two superstar players, Modric and Kroos, for absolute peanuts (50 MP combined) but what has been really impressive is their emaculate scouting. Varane 10 ME, Casemiro 6 ME, Asensio 3.5 ME. Just incredible deals for young players who have not only played vital roles in their success but will continue to carry them for the next few years.
Now is the second part of the scouting program, to transfer those young players from being talented partners to leaders of the team. The time has come to replace their old guard of Ronaldo, Ramos, Marcelo, Modric, Kroos and Benzema, it's upto those players (+ Kovacic and Isco) to take up their roles and continue the success brought buy their seniors.
With regards to the market right now, the World Cup added with the reduced transfer deadline has made it more difficult for premier league teams. Arsenal and Liverpool have shown great awareness of the situations and done their business quickly and can now rest easy knowing their squad is prepared for the new season. City maybe didn't require major overhauls given how they won last season, though even they quickly got one of their targets in Mahrez and failed to sign Jorginho.
United and Chelsea have been disappointing given how much change in the squad was required. United did well getting Fred and Dalot early but since then they have still left positions in the squad vacant and now the situation is looking more desperate. Chelsea, well, they couldn't get their manager situation sorted for so long so no wonder they haven't done anything with the squad yet.
Overall, I think it's just a situation of some clubs working more efficiently than others. I don't think you can relate United's struggles with other clubs in Europe because many have managed themselves well. There is a discourse between the manager and board and that has to be settled if United want to do better in the market.