It's more or less confirmed that McLaren turned him down because he was felt to be too tall and heavy.
He had a contract ready to sign from Ferrari until the whole Alonso gone - Kimi available saga started.
There really hasn't been a place available at Red Bull.
The same goes for Mercedes who btw wasn't much of a top team until perhaps last year.
So I think it's fair to say he is and has been on top teams radar but timing just hasn't worked.
Don't forget that drivers such as Häkkinen, Mansell and Button had to wait a long, long time for getting into a winning car and in Mansells case championship winning car.
mansell was in a winning car many times in his career. he was nearly world champion in 86 but a tyre blow out in adelaide cost him the title. button and hakkinen had to wait to get a clearly dominant car.