The reality is all players fit into 1 of 4 broad categories:
1) Proven Legends. These players will likely only not be selected due to injury or rotation. If they get into a bad patch of form they're likely to be played anyway in the hope they can play themselves back into form.
Examples in Current side: Anderson, Broad, Root, Stokes
2) Quality Place Holders. These players meet the 'international player' quality line and are capable of looking like they belong but are primarily selected on form. The thing these players all have in common is that they have shown they are capable of outstanding performances, but usually are unable to reproduce this form consistently enough to be automatic picks and earn them Category 1 status. This is a much larger category than category 1 and so players are picked on form/ match conditions.
Examples in current side: Bairstow, Moeen
3) Desperate Place Holders. Players who, were there half decent alternatives that weren't considered gambles, would likely not be selected. Very much 'for now' men. Capable of quality performances but rarely look comfortable at the highest level. They show just enough to make you think that they might be Category 2 players but ultimately are unable to banish their demons.
Examples in current side: Burns
4) The un-placed. Young players who are still developing and could therefore fall into any of categories 1-3.
Our problem as a media/ support base is that we categorise people far too early. Someone scores a ton and half the media claim that someone special has been found - but that's rarely the case. It is also the reality that in a good generation half your team will be Category 1 players (think of the Strauss era), in a weaker period (now) there is a much more even spread across all categories. You can't necessarily select out of this issue and the crux is that there isn't enough CC cricket to allow us to select on form. If we're honest Malan, Vince, Lyth etc are all category 2/3 players but we can't pick them based on form because we have no idea who is actually in form! This is also why the old hats like Bairstow continuously get selected ie they've shown they are capable of producing good performances and the chances of them coming into form are considered less risky than picking a Cat 4 players - plenty of people disagree with this approach but management of risk is particular to each coach.
This manifests itself in patchy performances because if half your team are category 2/3 players, for everyone that succeeds the other fails and this advantage cancels each other out. Conversely if they all fire on the same day you think you have a team of legends and are then surprised when two matches later they all fail and you get an absolute drubbing!