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 enmartialed items you can get Extra Attack, use a shield, action surge, Rage, and other useful martial abilities like that many times per day for a very reasonable price of 400 gold. For 4k gold you can get big ones like Extra Attack (x2) (especially good for wimpy wizards), Tactical Shift, Cunning Strike, Slow Fall and so on. Brutal Strike is considered one of the best abilities you can get, right? Sure, for 4k there is Cube of Brutal Blows! 10 charges, up to 2 Brutal Strikes per day (5 charges each). No Barbarian levels required.
Sure, you can always say it is but a fraction of full martial power. And you would be right. But it definitely does level the field. Because no matter how cool martials are they don't get spells. Most of the time they don't also get strong defensive abilities. Do you know how bad Monks actually are at keeping concentration? They often lose Str, Int, and Cha saves entirely and sometimes they negate one attack per round, but then get hit 5 more times and fail their concentration save. Same with fighters - with their front lining, lack of shield spell, and lack of a shield (they wanna do damage) they can't keep concentration for whole fight without trouble.
Stuff like Staffs of the Magi make it so having extra attacks, weapon masteries and appropriate feats like polearm master, fighting styles etc actually don't matter at all. Basically, any class without spells stops being comparable in single target damage to wizards. Half-casters and one third caster subclasses stop being comparable to wizards in single target damage. In other words, power levels of classes get much more reasonable (in casters favor).