Almost 10 years Man United did not win the EPL. Even 7 coaches have been selected to try to deliver the championship title but failed. After Sir Alex Retirement, Man United did look bad. In fact, many large transfers have ended up failing. When Ten Hag arrived, they began to improve even though they did not have a championship but Man United's performances were promising. They have made good use of transfers, but there is one player who could possibly be the solution. Since they currently do not have a number 9 striker, Maybe Man United can buy Kane as this solution. But Tottenham are unlikely to release Kane to an English club.
Arsenal is also one of the clubs that has not won a title for a long time. In fact it is difficult to compete in the Premier League somehow stop the dominance of Manchester City they are in a golden era. From what I've seen only clubs with old coaches can beat them like Liverpool so between players and coaches have a strong bond and built more than 5 years. Manchester United is far from this category they need a few more years to be stronger while Arsenal may be closer we can see the progress from year to year top 8 , top 5 and last season they were runners up I think in the next 2 years it will be Arsenal's turn.