There are 2 types of Gods:
The Otherworldly Gods, who reside in a different realm than humans, only accessible through extreme means that either involve taboo or death. They preside over natural things not found directly on earth (ie, the sun, moon, and stars, the weather, thunder, etc.), as well as Faith-Based Magics like Light/Holy and Dark. The access to these magics have been gifted to these humans by these gods, which is why humans like to say magic is a gift from the gods. They're referring to the Otherworld Gods
Then there are the Ancient Gods, who preside over various forms of nature. They reside on Earth and are almost always in slumber. Fire, Water, Earth, Air, Poison, Ice, etc. While these gods sleep, their essence spreads out over the earth and may inject themselves into humans, giving them natural magic ability. However, this magic is still borrowed from the god. These gods have been around for as long as Earth as been around, and are mostly invisible to being recognized by Earthen Denizens
Humans have always relied on magic to bring out the secrets in the world to make it a better place. Fire, Water, Earth, Air, Thunder, Thauma, as well as the powerful faith-based magics Holy and Dark to do the will of their gods. These magics have been used to make, preserve life, and preserve the sacredness of the land, whether that land is mountains, deserts, plains, etc. They've managed to expand themselves pretty well and advance pretty far while still preserving the world's gifts and nature
However, there are a group of people who believe that the age of the gods is over and that humans don't need them. They accused the gods of toying with them after creation, seeing them as entertainment, letting and even causing bad things to happen, like natural disasters. The leader of this group ended up becoming a king who plunged the world into a dark time by branding magic as heresy and taboo and sending the Church and the Inquisition after them. The preachings spread far and wide over time and Magic became the thing of scorn. Public executions for magic became a constant sight, par for the course, magic-themed books and epics were burned from libraries. This caused the Otherworldly Gods to shun Earth and eliminate access to their powerful tools. He then went about expanding over the entirety of the country, convinced that there are no ancient gods slumbering. Needless to say, in an excavation campaign, he stumbled upon one of these Ancient Gods and woke them up, angering them. This woke up ALL the Ancient Gods, and subjected all its denizens, innocent or not, to their wrath.
They cursed the humans and anyone who worked closely with them (humanoid species). They can't use magic anymore. That gift was stripped from them for their insolence and rebellion. That isn't to say humans were the only users of magic. The entire world has thrived on the mana from the Ancient Gods and in same cases even morphed or mutated. Enchanted Plants you can use to enchant gear, Magic-wielding Animals you could potentially tame. This also means that hostile animals are faster and stronger.........and with no magic of your own, far deadlier. With no magic to fall back on against stronger animals, enchanted Apex predators became apex even over humans. The economy suffered. Career Grand Wizards and Magic Advisors went out of business. Entire magic schools and magic colleges closed down. Magic military brigades disbanded. Apothecary shops closed. Lives lost due to having to adjust to not having healing magic.
There only seems to be one way to reverse the curse, as told by the Ancient Gods. Destroy their Titans and retrieve their essence. Taking their essence puts the Ancient God back to slumber and returns the magic back to the earth for all and the world to use again. It's not that easy though, as Titans are colossal beings that hold all the magic of an element. Any one Titan can wreak substantial havoc, so the Ancient Gods decided to show a bit of mercy and not release them. Instead, they put it upon them to activate them on their own. Where the Ancient Gods sleep, there is a sigil. Activate it to summon the Titan individually. Then defeat it. Defeating it unlocks that specific magic for use again.
With no magic to assist them, and having to fight forces sent by Gods, the Humans (and humanoids) of the Earth are fighting an uphill battle. Who will you be? A soldier on the frontlines? A seer who works as an advisor? A normal person just trying to make an honest living? What are your goals? What is your calling? No matter what, you'll likely be caught in the crossfire.
Think Shadow of the Colossus
These are massive, hulking creatures, avatars for all that's known about an element, whom you must kill armed with nothing but sword and bow, one's own wit and skill on the battlefield. Some Titans are unique environments upon themselves. Imagine a giant turtle with forests on its back that you must fight through to get to where you need to go to strike it, or having to take on the wrath of Poseidon himself at sea. Some environments are so extreme that they can't be traversed and you can't make it to the Titan Sigil without magic protection. You're little more than an ant to such power, but an ant's work ethic could very well prevail over all but completely impossible odds.