Taking my turn to breath. I want to chime back in once more...oh boy these are fun...
So there are various factors in the game itself that do NOT help. The biggest problem we have to account for is the game itself, I mean the big fat rulebook...well it lost a few pounds...stop fat shaming the rule book! The core of it is they are doing massive fundamental shifts in how special rules work along with almost everything in the game being changed.
Modifiers are now a common mechanic (AP rule...which should of just been written so they don't have to clarify what improve means everytime they want a rule to do so!)
Re-rolls have been lessened and in a lot of ways nerfed when they were common place.
Movement is no longer a mathematical chess game, there is variance to it. We used to have all sorts of calculations due to the "6 inchs to charge".
Shooting has in a lot of ways also become a different beast with split firing now standard to everyone and not just long fangs...I don't know who else had it prior to 8th
Assault is handled drastically differently and offers some interesting options and ideas (though rarely gets to in my experience)
Even how we calculate losses is overhauled drastically in relation to bigger units, with the new stat "Damage".
We have to look at the game as a whole and see all the changes and how volatile it really is right now. The game is still forming, evidenced by the fact we are having beta rules implemented into the game to attempt to balance it which is AWESOME. I welcome live fixing. The change to smite was nice (and the fact its final version was different from the beta, addressing a core issue with it, was excellent) along with how they fixed the character issue and now they are approaching the issue of the alpha strikes via deep strike (which aren't counterable with any really agency unless you play horde and at that point...well you didn't care anyway) and the over-souping of armies. I believe that since GW were open about the idea of 2 big updates to the rules each year via the FAQ and chapter approved says to me they were SURE themselves there would be things they missed that could cause issues. Come on, the character thing is not something you would expect as "Who would take an army of characters? That wouldn't work", a lot of what they are addressing is the extremes we as the community are able to show them.
This is evident in the fact that it seems that as codexes later in the rotation got better. However there has been historic evidence of marines always being first and always falling short later. Whether that is from codexes being written in response to those codexes or the writers getting better as they write more codexes having learned from their mistakes or even possibly a core underlying issue with marines? who knows, I am not saying there is a core issue with marines but as we have discussed there are a million possible targets for what it could be or couldn't be.
Within my mind, marines should not be cheapened nor should guard be taxed. Just give marines something to call their own really. However I suppose I should say this here and have had some chance to refine this:
Units should pay for their stats and rules, not their options.
Weapons should pay for their stats and rules, not their options (with consideration to availability being the only consideration outside of the weapons stat).
Best example of this: Imperial Knights Questoris Class Gallant. So, for all my fellow knights out there doesn't it seem odd that the Gallant is 285 points. The exact same as all the other knights. Remember, this is the points cost of the model itself not including wargear. It costs the same as an unequipped Paladin, Errant, Crusader and Warden. "It is to compensate for the melee only options", that shouldn't happen. The same, in reverse, happened to Devastator Centurions. In this case however, the Gallant pays 285 points, the same points the other knights pay, but for a superior stat line. (+1 attack and WS: 2+) which should be taxed as needed. The Gallant isn't any weaker than a Crusader as there are few shortcomings to the unit in terms of design: Is it fragile? Is it Slow? Does it have low output? No, all 3 of those are set to high, High Durability (T8 with 3+ and 5++ to shooting), High speed (12" movement is extremely fast for something that big. It is faster than a land raider and matches a predator) and the output of damage is extreme (we all know how good Knights are at Tap Dancing).
Right now, the game suffers from a lot of units not paying the correct points. This goes for marines as it does for guardsmen. To be honest, in guardsmen I will still stand by the stupid idea of how a weapon can cost differently DEPENDING ON THE MODEL THAT CARRIES IT! If we were still doing points based on the datasheets then that would be fine but if we are going to standardise with a table for weapons and models then everything on those tables now only pay for themselves, not who carries them (and vice versa with models paying for what they carry before they carry it).
This I feel would go long ways in improving the game and marines. Sadly, this idea would indeed cheapen marines and a lot of units outside of horde and thus see games get larger as a result but sadly it would at least give us some balance. Not an ideal solution, not saying it is but it would move us in the right direction.