And that is the complaint that people have against the Alchemist class, it serves no real required purpose.
If anything, Alchemists are more useful than any other craft.

All of the other crafts make item level 70 gear. Once you gear past that, that's it. They're done. You don't need that craft anymore.

Alchemists? Lol, they're useful ALL the time, at ALL tiers of content. Potions are useful from once you hit 50 to the end of Bahamut's Coil and Extreme Modes.

Where as ALC's potions are far less effective in use for their current CD's and effects making them a riskier investment for players considering content can be and has been regularly completed without them. This is what people I think are trying to get at when they are asking for changes to be made so that ALC has an equivalent level of viability to that of CUL.
I would say CUL and ALC's contributions to a fight are about the same. The total damage gained from using a food for the duration a fight, versus the total damage gained from using two potions (at the right times). Yeah, about the same, except potions also allow you to control when that burst of power is applied, using it at opportune moments in any given encounter (Titan Heart).

While yes, food may be a safer investment due to the fact that a wipe does not simply cause a loss of the item, potions are also a lot cheaper. I would say the amount of gil it takes to get a similar, good quality food for the course of X amount of encounter attempts is the same as it takes to afford X amount of potions for all those encounter attempts. If you don't want to compare gil, you can also simply compare the effort to obtain the materials; it matches up as well.

Like I said; it's not SE's fault people are misinterpreting and not understanding the effectiveness of potions.