Cool, so it's something that has always happened rather than a problem with the modern game, as others have claimed. You're saying it's a player issue, not a game issue. That seems reasonable. We all know there are players who like to hog the spotlight. But this discussion has been about that allegedly being characteristic of the modern game. It isn't, it's characteristic of selfish players which have always existed.
I would argue that while the selfish me-first players have always existed (and, sadly, always will), over the years the designers have slowly caved in to these players and thus the game as designed today directly caters to that selfishness far more than it used to:
--- lower character lethality and...
--- ...a big reduction to really bad effects on characters other than death e.g. no more level drain, item destruction, etc., due to...
--- --- ...a design chassis built on the philosophy of "once you have it you can expect to keep it"; the game gives but it doesn't take away any more, where once it was accepted that anything gained (levels, treasure, etc.) might not stick with you forever
--- greater expectation by design of being able to play exactly the character you've preconceived without having to compromise due to dice luck, alignment restrictions, or what other players are playing
--- greater expectation that everything is core and thus must be allowed (or put differently, it's harder for DMs to ban stuff)
--- faster and more frequent rewards, here expressed as gaining levels
--- greater power over and-or separation from the setting, expressed as the gap in power between a commoner and a 1st-level character
--- balance, expressed as every character has to be somewhat-equally effective in any situation
Will this trend continue as the editions evolve? Yeah, probably, because the squeaky wheel gets the grease.