I don't think there has ever been a successful United side that has not had at least one clinical striker. Perhaps the 92/93 team, but that was a team that had goals coming from all over the pitch. Players from midfield and even defence would regularly chip in with goals, making light of the fact that that early Prem United side didn't have a true out and out striker.
We do sometimes suffer for not having a striker who can be relied upon not to miss the tap ins and one on ones. That is compounded by the fact that not only Rashford but Martial can also be wasteful. It's also exacerbated by the lack of goals coming from other areas of the team. Our defenders are generally hopeless at corners and there are some midfielders who never look like scoring.
There is no way that RVN or Ronaldo or even Andy Cole or Dwight Yorke would have left that game without at least two goals to their name. Remember that nonchalant way in which they used to score hat tricks? That is what we are missing here. A player who can be relied upon to fill their boots in the nondescript, bread-and-butter games. Yes, Leicester are much better than that, but they were there for the taking today, and we blew it.
When Marcus passed up that opportunity, you just had flashbacks of Ruud gobbling up that chance. There is no way he would have let that chance go begging. Ruud needed to score, so did Ronaldo, and so did Cole.
Marcus is still a young lad and his all round game is improving all the time, but he has to become more clinical. Without having goals coming regularly from midfield and defence, we need to have a striker who can be depended upon to capitalize on one-on-ones and gimmes. That is what Salah does for Liverpool, he rarely misses those chances.