Power creep is a thing that I think we are all feeling. Also I play a lot of wizards when I’m not DMing, I never keep level 1 offensive spells prepped past Level 6-7, the only level 1 spells I’ll prep regularly are mage armor if Combat is expected, detect magic if we are exploring and I always keep shield prepped. But 1st level damaging spells are never again prepared because cantrips outpace them. Interesting question, does it bother anyone else that at level 5 cantrips do the same average damage, or more, than most 1st level spells? Hell fire bolt has a higher damage capability than any of them except chromatic orb, if you allow chromatic orb. Now level 1 spells are save vs. half and AOE, but still their limited range makes them less usable sometimes then cantrips. At level 11 cantrips completely out match level 1 spells. Had anyone played around with nerfing cantrips a bit to make them less powerful long term?

What I’m thinking, and I’m just spitballing here, is at level 5 instead of increasing the damage die adding the casters spellcasting mod to the damage and then leaving them alone as they level further. The spell casting nod would stack with clerics potent spellcasting, evocation wizards empowered evocation and sorcerers elemental affinity. But I don’t think that would throw things into the imbalanced category. The exception to the nerf would be eldritch blast because the multiple beams is part of the heart and soul of a warlocks offensive abilities.

What do you guys think? Is this a good idea to help reduce the power creep and keep level 1 offensive spells more relevant? Or am I grasping at straws and should just leave things alone?

This'd likely increase the power of casters by a fair bit at certain levels, as most spells come with a form of AoE. Consider a 1d10 on firebolt is on average 5.5 damage, so 2d10 = 11 at 5th. Hitting 2 enemies with burning hands at level 5 means you're probably going to deal 3d6 + 4 = 14.5 damage to both of them with a DEX save for half. when we move up to 11th level, fire bolt is 16.5 and burning hands is 15.5 to each target. Don't underestimate the powers of these features!

Level 1 damage spells falling off is maybe not the most elegant design decision, but it is integral to 5e. Low level slots will remain useful throughout the entire campaign, you already mentioned shield and detect magic, but other brilliant spells include absorb elements and find familiar. You just use your 1st level spells and spell slots differently, is all.

Do note that what lv1 spells have against cantrips are more reliability, and specific niches they could fill that cantrips do not - for one, AoE (Frost Fingers and such.), for others, multitargetting (Magic Missile, Catapult, Jim's Magic Missile), and many have damage types that are either rare, or very specific on cantrips that work on a very limited situation (Thunderclap deals Thunder damage, but it will always be stuck at a 4d6 at maximum under a Con save, and under a 5 ft. radius, while Thunderwave, Thunderstep and Shatter have somewhat better uses, and what is more important, scale up by the spell slot you use.

You also simply don't beat Jim's Magic Missile "possible maximum" damage, at a whopping 60 at level 1 (assuming you suddenly roll all 20s and 4s) - you also have semi-offensive spells like Absorb Elements, which despite being able to deal damage, it stays reliant on your own defense.

Cantrips (maybe Eldritch Blast only) don't powercreep level 1 spells. Higher level spells powercreep level 1 spells - why cast frost fingers when you can cast a cone of cold? why cast thunderwave when you have shatter? why cast such spells that you wouldn't really use because other spells are way more reliable?

Yeah, I think the point here is the higher you get, the more you can choose to use lower level spells for utility and versatility, while the cantrip scaling makes sure you can still do a basic attacks that aren't useless.

The cantrips might outscale the lower level damage spells, but like I said that is just so you should be able to skip using low level spells for damage. 

You prep lower level spells so that you can cast them using higher level spell slots. A 4th level Chromatic Orb hitting for 6d8 damage is better single target damage than many other spells, and can get around resistances, and a Sorcerer who twins it is doing a ton more. And a crit is even juicier.

Magic Missile is the most certain direct damage in the game. If you aren't prepping this when you have it available, you're making a mistake. It's rough being a player and hearing than "He casts Magic Missile on you, at 6th level. That's 28 (8d4+8) force damage, no save, no attack roll and in a single target boss fight, usually your best damage dealing option is to cast Magic Missile at your highest spell level available and then work downwards.

Hold Person followed by Inflict Wounds is pretty dangerous.

Always look at what you can do with these spells when you upcast them. Sure, blight deals 2d8 damage more than chromatic orb when cast at 4th level, but you have to use a 4th level slot on it. You might want to hold onto that for something else, and cast a Chromatic Orb at 3rd instead.

I actually think that there's great versatility in spellcasting because level 1 and 2 spells actually never drop off.

Cantrips are fine as they are. Why wouldn't you want your cantrip to deal reasonable damage? It's not as good as a comparable level fighter etc.'s melee attacks, but it's ranged and it's free so that seems balanced.

You can't really do a fair comparison of cantrips and level 11 vs a lvl 1 spell cast at lvl 1. The caster has so many more options at that point.

Cantrips fill a need and are a FAR better choice than not having them at all. More than half of them used to be 1st level spells. Imagine having to prep that.