... if it's just an idea.

Way too often people post their undercooked magic "systems" asking for more input while only explaining the bare flavour of their magics.

Saying that they use elemental magic through hand gestures is not a system. System needs some sort of framework of rules, abilities and restrictions, defining characteristics how the magic works.

So. Make them use elemental magic only when in direct contact with that particular element. For example they have to be in the water, like stick their foot in the filled water basin, to be able to cast a spell through complicated hand signs. Now we already have set some basic rules: contact and hand signals. These also serve as restriction. Spellcasting without one or the other doesn't work.

How does the magic work? Being in direct contact helps you translate the essence of the element through the hand signals, and give the element a new form.

But what kind of spells can they evoke? Make it rain or conjure a water cannon? These desicions specify the magics to a greater detail and they too need some sort of limitations. How great of an area will the raincloud cover for example.

This is pretty much a bare minimum to consider when talking about a magic system.

Or am I wrong and just a nitpicking twit?

EDIT:

No. You don't need exposition dumps to explain to the reader how your magic works. The system is for the author to use as a tool. Just because something is not explained, doesn't mean it has not been worked on.

Doesn't matter if it's a hard or soft system, or how detailed or vague it is, it should still follow at least some sort of ruleset within the possibilities of the created world. System just means that you have figured out how it works in that word.

Moreover my point was that too many people here are talking about their magic systems without realising that they don't actually have a system. Got nothing against people who don't want to use a system or a method or a tool that could help them write. They have their own ways and that's ok too.