Good points. As usual I largely agree with a few differences here and there.
In GW1, cacti being the only sniper saw them be extremely annoying and often getting vanquish master on G&G matches. They were less of an issue in other game types although very good at defending the taco in taco bandits (a mode I miss as you can't get a match of it on PC anymore, I can get G&G matches but not mixed mode or other specific modes anymore). I'm not a huge sniper fan and never played TF classic but do have over 400 hours in TF2 and Sniper was my least played class, and rocket jumping up on the sniper ramparts in 2 fort as a soldier and wiping out the enemy team snipers was a favorite past time!
I'd say that GW1 maps were a little too open usually and cacti could be a nightmare if they were decent at it. GW2 maps now had to deal with with 2 sniper classes (and variants and of course frozen citron being the best sniper till they nerfed citron's long range damage), and overall I felt snipers worked well there without feeling oppressive. In BfN barring the one guy who somehow gets on top of ludicrously high terrain that I can't seem to get to and never see anyone else do it either (like the really high rocks at the start of goopy gully as a deadbeard), I don't feel the maps are as bad as you report but the charging mechanic is too much like Widowmaker from OW, and I preferred the old style for their weapons.
The TT maps in BfN are too narrow and lack the fun back and forth fighting we had in GW and GW2 thanks to the change in design, so snipers do lose some value, but they can do well and be effective. I feel the payload has to provide some cover as it already means that your team has to have people on it as often as possible to move it which paints a big target on you, and I've sniped at whatever I can see as they all have gaps to shoot through/over. I'm not a huge fan of the payloads in the first place though, I'd much prefer TT maps like in GW and GW2 instead.
Drones are so slow in BfN and their weapons all feel awkward to use, which is a common issue in BfN combat in general. Potato mines should lose that flashing light (remember when people were concerned that the bling mines were too easy to see in GW2?), the 2 mobility abilities need to work better (anchor's away is better, but like rocket jump and swoop slam the movement and camera of these movement abilities is just off in BfN), and they should revert barrel blast to more like how it worked in GW2 where it was hard to cancel but you could by vanquishing the armored pirate inside (and got bonus xp too). Giving Cactus that Gatling needle like the Bandit Cactus has does help them with close/mid range combat, which they are mostly awful at in GW/GW2 and let them compete there better with Deadbeard's shotgun. My biggest dislike about the snipers in BfN is them using the same weapon that is mostly Widowmaker's rifle instead of having their own unique snipes like the GW games which I vastly prefer.
Overhealing is an issue in general in BfN and is compounded by how powerful healing is, yet a lot of veterans don't like Sunflower as much as the GW/GW2 versions. I know Asabaida left the game partially due to that. If they pull it for the new game, I'd be happy as I don't hate it in TF2, but it's not a huge factor all that often there, where here it is.
As for the scope glow. I actually just watched a YouTube video about why games have that and while I agree it's weird for the cactus as far as why it would exist, it was meant to be mechanic to help spot them as we don't have the sighting icons from GW2. I tend to snipe and move a lot so I can't be caught too easily. As for the reduced view, a lot of games seem to do that when sniping, and it's meant to punish those that aren't aware and spend too much time in their scoped mode.
If they reverted sniping to how it is in GW/GW2, made the mobility abilities better as Cannon Rodeo is another turret mode and we have so many already and the Wall-nuts aren't all that effective, fixed and balanced the drones, and made other QoL changes, I'd be pretty happy with Cactus and Deadbeard in the new game; i.e. GW2 versions with the mobility abilities working fully.
