Martial-caster divide is not that bad if you let your players buy and sell magic items without hassle.
I play at the table where we use exclusively 2024 rules. Since these annoying rules about buying magic items taking several weeks and additional costs are technically no longer a thing and were replaced by just a couple of simple guidelines and costs, our DMs just let us buy and sell magic items without trouble. So, any large enough settlement just has a vast enough market of magic items that you can just buy or sell them for the listed cost
Uncommon items are 400 gold, rare items - 4k and very rare 40k. Legendary ones are the only ones not for sale.
So, to the point. Apparently, at our table martial-caster divide kind of does not exist. With enspelled items you can get Divine favor, Shield, healing word, hex and other useful spells like that many times per day for a very reasonable price of 400 gold. For 4k gold you can get big ones like haste (especially good for rogues), spirit guardians, counterspell, fireball and so on. Wall of force is considered one of the best spells you can get, right? Sure, for 4k there is Cube of Force! 10 charges, up to 2 walls of force per day (5 charges each). No spellcasting ability required.
Sure, you can always say it is but a fraction of full caster power. And you would be right. But it definitely does level the field. Because no matter how cool spellcaster is they don't get second concentration. Most of the time they don't also get strong defensive abilities. Do you know how good Monks actually are at keeping concentration? They often negate damage from Dex saves entirely and most of the time they negate one attack per round, reducing damage to 0 and avoiding concentration save. Same with fighters - with their armor proficiencies, shield spell, con save proficiency and additional feats they can keep concentration for whole fight without trouble.
Vicious weapons make it so having extra attacks, weapon masteries and appropriate feats like polearm master, fighting styles etc actually matters a lot. Basically, any class without extra attack and weapon masteries stops being comparable in single target damage to martials. Half-casters and extra attack subclasses stop being comparable to Fighters in single target damage. In other words, power levels of classes get much more reasonable.