This is the issue you are judging the skill sets on what you believe is what we need, not what Koeman believes best suits his style and approach to football.
Of that list Milik is the only one who remotely resembles what Koeman likes in a striker and injury aside he's hardly lit up the serie A. As for the rest Correa, Vietto have failed to move an ageing Torres out of a striker role at Atleti and have to play support roles from out wide / off the bench or have been moved on. Fekir similarly isn't a lone striker he works best off of a striker either centrally or again out wide. Werner before this season had accomplished nothing of note and spends most of his time playing alongside a powerful striker who takes the burden of what he doesn't possess physically therefore not ideal for what we need but a good young prospect in a different system.
Belotti is the only one of them good enough to make the move to the prem currently and lead a team.
Benteke is perfectly suited to Koeman's style, he's strong, very good hold up play, far better with his back to goal than Rom, a genuine threat aerially and most importantly brings guaranteed premier league goals. His goals to game ratio compared to Lukaku since 2012 is 42% to Roms 47% which is impressive considering his injury issues and horrid time with that lot which massively reduced the amount of goals he scored due to not suiting them stylistically. Here he wouldn't have that problem, for all purposes he's a better version of Pelle and Koeman worked wonders with him during his time at Southampton and Feyenoord.
Our list of targets that suit Koeman and are well known names is small, in the prem alone only Giroud and Benteke fit the criteria that are good enough and realistic targets, outside the prem it's a complete gamble on players like Willian Jose, Modeste, Dost, Raul Jimenez, Babacar all not really well known names but linked because they fit the style more than a Belotti, Icardi who would be great signings but not to directly fit Koeman.
One name your spot on about is Mario Gomez think had he been 4/5 years younger he would have been absolutely ideal for us and the direction we are heading.