The comparison between Shroomite and Spooky is a bit funny, though, in terms of attainability Shroomite is much closer to Tiki instead. It's just that it never gets a straight upgrade, and doing hybrids with sentries is largely ignored here as otherwise that just gets put down on summoner's resume too. Ballista Panic is also annoyingly easy to activate for something that somehow makes Ballistae do even more DPS than Explosive Trap despite also having better range for bossing.
Though going back up to Sandgun, I recognize that the weapon is a bit unwieldy with placing sand, not everyone wants to place minecart tracks to prevent sand placement, but in terms of saying that it was a best weapon against the Goblin Army, this was referring to the fastest possible kills. Once you have a decent weapon and decent mobility, and can consistently stay out of the way of archers and sorcerers, the Goblin Army isn't going to kill you and it just becomes a matter of what gets the fastest kill. Sandgun, with its infinite pierce no damage dropoff coupled with range that extends outside the screen, and Grenades, which also have all these properties when you consider range extends down, too, are tools that can kill the Goblin Army at the absolute fastest rate, spawning Goblins at their full rate and killing them as they are spawned for the theoretical fastest possible completion of the event. The setups for this are a bit silly, in both cases this involves roping up to build better geometry and for Grenades this is a pit while for Sandgun this is a straight line with torches or tracks at the end, if you don't do this setup you aren't going to get the absolute fastest kill, but I bring this up in response to summoner's damage numbers for goblins being mentioned. Snapthorn and minions do deal a lot of damage, but I wouldn't say that's the most important metric here, as if your only goal is to kill the event as fast as possible, a Grenade pit farm is as fast as it gets.
The reason I brought up jungling is that, yes, it is a very useful place to go, but I would actually attribute this to its open generation and abundance of chests more than anything else. Boomstick is a strong gun, but other guns are plenty good and easier to get, Anklet of the Wind is convenient but I don't like the money cost for reforging Lightning Boots. Staff of Regrowth, yeah, no real way to replace the sheer convenience there besides more time spent farming. As an experienced player, I can go in the jungle early and get lots of chests and a honey bucket and lots of life crystals quickly - if I have a good enough weapon, I might stick around and kill enemies for a blade of grass or axe of regrowth.
For a less experienced player, yeah, they can jungle with the support of a flinx staff and leather whip pretty well, albeit hornets could be an issue with limited range. They could also just use those tools against the Goblin Army, Flinx Staff is indeed plenty of damage for that fight and if they were really scared they could block themselves in and just use the whip to snipe chaos balls. The requirement is never the best, just what's good enough, especially when talking about an event that just shows up at your front door one day with just a couple minutes of warning. When jungling, yeah, ranger is the class that gains the least from jungle loot in the context of Goblins and the evil bosses, no Snapthorn, no Blade of Grass, not even a unique armor set. On the flipside, ranger suffers the least as you start peeling off gear and progression, since Grenades are always there, while you had to make the choice to jungle. That is a choice I will almost always make, but in a recent poll on the official Discord server, 54% of players from a poll of 4,000 said that the jungle/underground jungle is the most annoying biome to traverse in pre-hardmode. The corruption, and thus shadow orbs, was 3rd place at 13%. A lot of players don't make that choice, or at least seem to dread it - underground desert was a distant 2nd at 15%.
Also, I have a personal hatred of Ivy Whip because I can't stand multihooks. Very inconvenient for building. This is pretty personal, but that is why I just don't consider Ivy Whip at all when I'm considering jungling loot. Really I go in early for Staff of Regrowth, potentially grab Feral Claws right before evil bosses or Skeletron if I want to use melee for those fights, then post-Skeletron if I don't have enough spores for Void Bag or don't have Feral Claws for Berserker or Mechanical Glove I go in again. Post-Skeletron is actually the stage where the Guide recommends jungling, which is quite funny considering that he recommends specifically fighting Queen Bee after the evil boss without considering Skeletron there.