Yes, but a lack of mechanics inherently eliminates some of the more magical choices such as shifters and changelings
Not necessarily. It really depends on how free-form the DM (and the players) are willing to play
without requiring dice rolls to do things, and instead just act and make decisions in the manner that the species features suggest.
If someone is playing a shifter (for example) and their species feature is that when they shift their form they become more bestial and wild... the player can show that off by making choices in-character that are just more chaotic or more animal-like that they do when their PC hasn't shifted, so that their actions and what occurs denote them being more bestial. For example, a bear-like shifter player decides that when their PC shifts... the PC is more apt to run into melee combat and absorb attacks in hand-to-hand that their PC might otherwise not when not shifted.
Now of course the issue for a lot of players is that they look at the game from a meta and top-down perspective... and
not from just what occurs in the story. They would say that with no mechanical change in the statistics of the PC, then the character isn't becoming more bear-like or tank-like when they shift because the numbers are no different than they were before. The non-shifted PC is exactly like the shifted PC so the so-called "shifting" has no actual effect to the game... it's merely in the "imagination" of the player(s). We're all
saying that the shifter has shifted based on how the PC perhaps acts differently... but action without mechanical change is not meaningful for a lot of players.
It's the same way that some folks think that an elf that doesn't have a +2 Dexterity built into their species write-up isn't truly more agile than other species. They need that +2 Dex in order to get that across that elves are all more dexterous. Nevermind the fact that the player could just take actions to show off how "agile" the elf PC could be-- purposefully running across rooftops or jumping and swinging from chandeliers, or taking more Disengage actions to get out of melee combat moreso than other players have their characters act... for many players those things "don't count". Because it's not the narrative of what actually went on in the story, but what the game mechanics actually are that tells them what the reality is. I mean I argue with other folks here about this sort of thing all the time when I ask how could a +2 to Dexterity in the elf species write-up actually matter when the player can still end up playing a elf PC with a Dexterity of 10 while the player of the dwarven PC has a Dexterity of 16? That elf numerically and mechanically isn't more dexterous for being an elf... so what did that +2 in the write-up actually get you?
At the end of the day... it's all about a person's perception of their game. Are they someone who sees characters sheets and the mechanics therein as an actual indicator of the reality of the world... or are they someone like me who thinks only that what actually occurs during play is "real" (within the story) regardless of what our character sheets say? Because to me... even if a character sheet
says I can do X... if I never actually do X during gameplay, then to me X doesn't exist. Or if my sheets says I am Y but I never act in a way that indicates I am Y... then as far as I'm concerned I am not Y. That's my perception and how I wish to play the game. But obviously there are hundreds of thousands of other players who perceive it differently. And that's totally okay.