hey sorry i don't want you to think this is specifically aimed at you but i see this frequently enough and i just want to say i don't understand the obsession with minion mixing that people seem to have
every other damage archetype gets a new weapon and just... gets to use it. why do people want summoner to have to keep using old weapons when we're already doing that by stacking whip tag effects?
like, why does melee get to just swing a terra blade without being told "no actually you should have to keep a bananarang and a light disc around to maximize the dps of your terra blade" but people want summoners to have to run around with 2-3 of each of their most recently available minions instead of just.. using their most recent minion?
It's not accurate to compare Summons to other class weapons, because Summons are something you pretty much just summon once, and then they remain as long as you're alive, you aren't constantly using the weapon mid-fight. It doesn't take much thought to think "okay, just summon 3 spiders, and then use another minion for the rest" etc. Other classes have some issues with iframes too, but it's mainly just Ranger since with some bows like the Tsunami, most of your damage is wasted because of certain arrows having longer iframes or using global/static, which means not all the arrows deal damage per shot, and the same happens with Crystal Bullets also.
Summoner weapons work a bit differently in that Firecracker provides a special bonus that is relevant all throughout the game for certain heavy hitting minions. Much like how Golden Shower can be used on any class for free ichor, or every class can use Betsy's Wrath for the additional armour stripping, or every class can use Vampire Knives to heal, etc. Summoner can use old weapons because they're still actually viable and serve a purpose, much like the above examples, at any stage after you obtain them. The only way to remove this all as a concept is to stop worrying about min-maxing, because it's not necessary.
Minion mixing is more important in a vacuum under the assumption that all your minions are attacking the same enemy at the same time and constantly.
If you have 3 spiders, they each have their own sprite which indicates their own iframes.
So, 2 spiders with the same sprite can't hit the same enemy at the same time.
But this probably isn't an issue when you consider that the big enemies you're hitting will move around a lot, and it's not guaranteed it'll be hit by the same spiders at the same time.
Generally, all the stuff about whip stacking, minion mixing, and high-level strategies are optional. You can beat the whole game without whip stacking or minion mixing if you really want to, it just won't be optimal, and some people really like to min-max.
Summoner is inherently more complex than other classes because it has more mechanics than any other class.
Melee, ranged, and mage all function the same - point and click.
Melee gets tankier, and generally has easier weapons to use, flasks, and moves faster.
Ranged has different weapon types, versatility through ammo, and the most advanced their gameplay gets is learning a new weapon trajectory.
Mage has powerful set bonuses and the most utility, and almost all weapons in the class are unique and quirky.
Summoner has sentries, minions, whips, and mounts, whip stacking, flasks, minion mixing, etc.
tl;dr the things people say are mandatory for Summoner are just min-maxing tips and not required to beat the game or play well