You definitely aren't wrong!
There's way more to algae than light. What algae usually results from is something not balanced in an aquarium--and this is a bunch of things. Too much light, light too long, too much nutrients, ironically too little nutrients, not enough plants, problems with CO2 levels, etc.
To expand on it (this may be a novel, apologies), it's such a complex thing. Most usually start with the lighting or simply only suggest lighting. That's only one potential cause.
And then, certain algae tend to be more common due to certain reasons, but still aren't an exact science.
A small amount of algae is healthy and normal in any balanced tank. It's when someone becomes overrun that it becomes a problem that has people running for help.
Let's consider the other factors before reaching the light topic.
Let's talk nutrients. Often people automatically think of nitrogen (ammonia, nitrite, nitrate) being the culprit here, which is not necessarily the only nutrient involved. Some algae are especially fond of phosphate. People who struggle with algae regardless of trying all the lighting fixes and such should take a look at their phosphate levels. Especially if the algae they're getting overrun with is cladophora algae. It can grow short and tufty or long and straight, resembling hair algae--except it's coarse in texture and harder strands. This algae thrives in low light tanks, even shaded out by floating plants. It is a phosphate loving algae. I have an issue with this algae, thanks to the pH product I need to use in my tanks being a phosphate based product. Cladophora is rampant in my tanks, but, I choose to use it as part of the setup instead of trying to exhaust myself fighting it. However, understandably, not everyone is going to take this approach and will want to get rid of it. In this situation, trying a phosphate absorbing filter media is helpful.
Too much nutrients from extra fertilizer can trigger algae blooms, and if you have only a few plants, you may not need the entire dosage of fertilizer that the bottle recommends. This should be a guideline, one that you can tweak if need be. There's two methods: reduce how much you dose or add more plants. In fact, adding more plants often helps outcompete the algae if nutrient excess is the cause.
Then there is the opposite end of the spectrum where you aren't giving enough nutrients and the plants aren't thriving well--algae is more resourceful and will take up the scant nutrients better than ill-faring plants will. So someone in this case may consider boosting their fertilizer to see if the plants bounce back and start outcompeting the algae. This method obviously involves consistent removal of the algae manually in order to help the plants recover.
And then this also comes down to your source water. Everyone has different nutrients already available in their tap water. Different levels of some, some missing altogether, or some even in excess. And most of these aren't easily tested. So, look at your fertilizer, if it isn't working well for you, try another fertilizer that may have a different ratio of nutrients and see if it works better for you. Or, add an individual nutrient in addition to your usual fertilizer (i do this with my tanks with Java fern, I add extra potassium on top of my usual all in one fertilizer). We can recommend good brands of fertilizers that "generally" work for most people, but even these aren't a 100% perfect solution to every tank given the variability of people's water source.
To further elaborate on this, even various tanks within the same household will see different needs. Plants will use different nutrients than ones in another tank, and could lead to deficiencies in nutrients while another tank the plants don't utilize as much of that nutrient and have a surplus. Depending on the severity, this can also lead to an imbalance.
Some algae will take advantage of less CO2 in the water where plants may struggle to obtain the amount they'd prefer. Algae such as staghorn algae and blackbeard algae are notorious for this. Often times, the only way to really eradicate these algae is by installing a CO2 system. While many plants will do fine without a CO2 system, CO2 offers a boost in growth for plants, allowing them to uptake nutrients faster, which in turn outcompetes the algae easier. That said, it also isn't something to run into willy-nilly because CO2 has its risks and important things for people to learn and manage, plus it comes with a bit of a price tag. Anything "liquid carbon" is also a gimmick, these are often something that strips something in the plants, which can allow easier access to CO2 already existing in miniscule amounts in the aquarium, but not enough to truly do anything and can be harmful to fish and plants in the longterm. BUT, the liquid carbon (common brand is Flourish Excel) can be used as an algaecide to kill stubborn algae with a spot treatment quite effectively. It does have its uses, but not for what it's marketed for.
Lastly, light. Plants only need 6 hours of light a day. For folks having issues with algae, especially hair algae, they should consider reducing their light time first. Pay attention to stem plants especially--they will often close their leaves when they've had enough light for the day. It's a good practice to watch for that and turn lights off when the plants have said they've had enough. This is usually in 6-8 hour bracket.
If reducing light time does not work, then it's best to look at light intensity. One could either dim the lights if the lights they have are adjustable, or raise the light higher above the tank to reduce the light intensity that reaches the plants. Or, buy a lower light level if you'd rather go that route.
Light is a big factor in algae growth, but it's not the only factor. It all comes down to something being out of balance and this balance is one of the most frustrating things to find when getting into this hobby. And even once you find balance, if you change the tank (rescape, remove/add plants, etc) you can find yourself trying to find that balance again.
And getting livestock to clean algae isn't the best solution in these cases. Not all algae are even eaten by most livestock used for "algae eating" since most of these will eat soft algae and biofilm. More livestock adds more bioload to the tank which can ironically make it worse, especially since many chosen are mostly herbivores which have long digestive tracts which also means lots and lots more poop.
Cladophora algae, for the win
I can't beat it in my situation, so I embrace it in naturalized setups
What you don't see in many of my tank photos is the algae before I pull it! Every week in just my Paraguay tank, I tear out handfuls of cladophora algae. Every. Week. And it has to be manually pulled.
Probably will go from 10 hours to 12 hours a day with lights on and run 2 light tubes which the hood can hold.
