I would like to see what a "good" progression/unlock system means, since by definition this means that because you have played the game for an arbitrary length of time/kills/points/etc you are simply better than the newer player at doing things.
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*on this note, but less related to ro2, sidegrades are a grey area, especially when they are significantly different - why should the player spend time using a crappy gun/playstyle they don't like trying to unlock one they do?
Good progression/unlocks would reward players with, as you brought up in the end, side-grades and cosmetics. So perhaps progression is a misleading word since nobody would truly "progress", but rather, just get whole bunch of side-grades and cool looking costumes or whatever. But people still call them progression system because they still attach some sort of ranking to you which has no relevance to how your avatar/character performs.
I'm not sure why you brought up "crappy gun" when you mentioned side-grades because by definition, all guns are equal and the gun you start off with would be anything but "crappy".
Not perfect but a decent example of this is done in BF3 where your starter guns, especially the M16/M4, are the most user friendly and arguably the best weapon there is. Poor example of this would be RO2 where your character gets straight up stronger than newer character, or BF3's vehicle where unlocks are again, straight up upgrades. Still it's bit less offensive than RO2 though since you can get unlocks so fast in that game. To give perspective of just how time consuming and newbie unfriendly RO2's unlocks are, in BF3 I clocked in about 105 hours and have all guns unlocked, all unlocks for IFV/AA/Tanks, all attachments for 20+ guns, etc. RO2? 120ish hours clocked in and only got MG32 to level 50 (and that's after shameful bot farming). Highest level I got from normal play in that 120 hours is DP28 at level 36. Rest are lvl 0 or 19ish.
I read that CoD:BO did it even better by awarding players points, which can be used to purchase any upgrade meaning that you were allowed to get your favorite attachments pretty much on the first batch of unlocks. But I never played that so not sure if the same falls under guns.
Gotham City Impostors also let you choose your next gun/attachment and you get separate coin reward for cosmetics, so no need for "farming" to get your favorite guns (something that BF3 is guilty of) and looks either.
I guess GCI does the best form of progression/unlock. In GCI, you can have your favorite selection of weapon/perks in about... 2~3 hours of casual play?
RO2 and Tribes Ascend are two big culprits of bad progression/unlocks as both feature stuff that makes your guy straight up stronger than lower level characters.
Edit: Oh and if you think having more incentive to play because of progression/unlock is silly... remember the whole idea of video game is that it's just an illusion. Nothing tangible is being accomplished when 99% of gamers play. So what's wrong with enjoying these silly bonuses when nothing about it is serious?