@Vincentius TLR
The creation of one technology did not negate the advancement of another more "outdated" one. Take for example the bow and the crossbow. Sure, crossbows have only been around for like the past 3000 years and bows existed long before the invention of the crossbow but that didnt mean people stopped using crossbows. In a lot of cases a bow was preferable to a crossbow, it's why the English longbows became so famous even though crossbows were widely used at that point. War bows took a lot of time to train with compared to a war crossbow which is why they were used. The Cannon and later hand cannon were not developed to replace the crossbow or bow and it took centuries after the creation. The earliest firearm that you could consider even remotely close to how muskets work is the matchlock. And the matchlock wasn't seen as a long range weapon such as a bow or crossbow, more of a close range weapon that would let the user, more often than not, puncture even the most sturdy plate armours at the time, something bows and crossbows had trouble with.
The reason I bring all that up is because it isnt like playing something like civ where you need to unlock previous technologies. If your bows and crossbows cant pierce armour then you either make better ones or if something with promise comes along (such at black powder) you can make an entirely new weapon to deal with your problem. Now if you apply that to a world where magic exists, if in war people come up with more and more ways to defend effectively against magic then it would make sense that both stronger magic and alternative (possibly more effective) ways to wage war would come about. If that fireball you can throw is easily blocked or deflected by who ever you're fighting, why not try to hit them really, really hard with something (which might evolve into hitting them with swords, axes and any other melee weapon you can think of) or throw something really, really hard (then they'd probably figure out how to throw stuff really, really hard, such as slingshots, bows, crossbows and eventually guns). Once those ideas form people will realize that such tools are helpful in not just fighting as well, and if a tool can do it why learn how to use magic when using the tool could just be as effective if not more so.
You'll still have people trying to figure out how the world works so the sciences will develop, technology will develop on both the knowledge the scientists discover as well as the natural tendency of humans to make stuff easier and easier, since why waste magic power (thus your energy) on something when you could develop a way to do it with very little input like the time people made water wheels or windmills to help make flour. This is all assuming everyone can even use magic in the first place, let alone if they can all use it equally well as each other and as @twinklecake said that they've spent the time and effort into being able to use it. That's another thing technology has done, it allows people to live equal lives regardless of physical capability. You would assume that should a society be allowed to progress for 50000 years the people of that nation would move to make life easier for themselves, allowing them to start to specialize (like how most modern society works) and that even without the magic the technology developed would be stuff we today could never imagine as being possible.
People are both inquisitive and always looking to make things better for themselves. If they live within their means they'll probably be easily bored and looking for something to do once they have done what they need to in order for their continued survival. They will try to figure out how the things around them work and use that to make their own lives easier. This leads to technology being invented and society progressing forward regardless of what other things exist around them.
The reason I bring all that up is because it isnt like playing something like civ where you need to unlock previous technologies. If your bows and crossbows cant pierce armour then you either make better ones or if something with promise comes along (such at black powder) you can make an entirely new weapon to deal with your problem. Now if you apply that to a world where magic exists, if in war people come up with more and more ways to defend effectively against magic then it would make sense that both stronger magic and alternative (possibly more effective) ways to wage war would come about. If that fireball you can throw is easily blocked or deflected by who ever you're fighting, why not try to hit them really, really hard with something (which might evolve into hitting them with swords, axes and any other melee weapon you can think of) or throw something really, really hard (then they'd probably figure out how to throw stuff really, really hard, such as slingshots, bows, crossbows and eventually guns). Once those ideas form people will realize that such tools are helpful in not just fighting as well, and if a tool can do it why learn how to use magic when using the tool could just be as effective if not more so.
You'll still have people trying to figure out how the world works so the sciences will develop, technology will develop on both the knowledge the scientists discover as well as the natural tendency of humans to make stuff easier and easier, since why waste magic power (thus your energy) on something when you could develop a way to do it with very little input like the time people made water wheels or windmills to help make flour. This is all assuming everyone can even use magic in the first place, let alone if they can all use it equally well as each other and as @twinklecake said that they've spent the time and effort into being able to use it. That's another thing technology has done, it allows people to live equal lives regardless of physical capability. You would assume that should a society be allowed to progress for 50000 years the people of that nation would move to make life easier for themselves, allowing them to start to specialize (like how most modern society works) and that even without the magic the technology developed would be stuff we today could never imagine as being possible.