The rules have changed about strikers and look at the best teams in the world currently, your traditional striker is much more than someone who just plays down the middle. The expectation is they can play anywhere across the front three dependant on what or where the other two are doing.
The problem with modern football is that loads of pseudo-tacticians talk of meta-shifts in terms of how a striker is supposed to play, and use buzzwords like playing across the front three and whatnot, even though the basic plan hasn't seen a transitional shift (unless one is talking about pure target strikers). There is no expectation to play across the front three. Most top teams still have strikers who engage the central defenders, and the positional interchange isn't as everpresent as it's portrayed to be.
This is a standard Lewandowski heat-map at Bayern, and he plays essentially the typical #9 role. He drifts at times, and comes deeper - centrally; but doesn't have positional interchanges with Costa or Coman or Robben:
This is Agüero's heat map at City. Again, drifts a bit, but his standard action zone is in central forward areas:
This is a typical Suárez heat map. Again, central action, leading the lines, extending the defense, and creating pockets for Messi and Neymar.
Karim Benzema at Madrid - acting the foil to Ronaldo:
Van Persie at United:
All of them are predominantly active in central and deeper central zones, as has been the case for strikers and forwards for donkey years. There's no monumental shift in the way they play. Or Diego Costa at Chelsea, Mandžukić/ Morata at Juventus, etc.
And this is a sample Zlatan heat map:
Reading your over-emphasis on fluid front threes, one would imagine Ibrahimović's heat map to resemble Duncan Ferguson's - but he is much more than a striker. He recedes into deeper areas to link the play like a false 9, creates room for Cavani, leads the line, and much more. You'd have little to no trouble building a smooth attack with Ibrahimović.
And just to sample how he plays these days, here are bits of his match vs Real Madrid to highlight his movement:
And this is how he operated over the month of March last season:
Notice the deeper patterns where he links up with the midfielders, and creates room for Cavani.
The pool is shallow for traditional strikers cause they are no longer a requirement.
I honestly don't understand what you mean by traditional strikers. If by traditional you mean strict targets, then the good news is Zlatan is not a target type.
I have no interest in Zlatan and the circus that comes with him.
Now we've sidetracked from semi-objective to subjective debate, and I honestly have no appetite for it in FF. You don't know Zlatan on a personal level, and how he acts with his team-mates, and neither do I. So these are uncertain terms.
Also I have interest in paying him 300k a week, for yet again a player that's at the end of his career, when the Marial's et al and worth the risk.
Luckily United have money to spend? Rather 300k on a worthy risk, than that money in the bank - and no solution to our striker conundrum in sight.
Can we stop buying players based on reputation and more the young'ish players that are also wanted by the other top clubs.
The key thing is - Zlatan's reputation is current. And he's scored close to 50 goals this season at club level, and almost 1 per game for Sweden. No matter what way you spin in, the tag of him being a pure reputation based player can't be justified. Say what you will about Ligue 1, but a handful of the best player in the Premier League were plying their trade there just last season. And Zlatan's better than them, a physical beast (would dwarf a good deal of Premier League defenders), productive, immensely proud - which could rub off on our oft-shellshocked players, and experienced.