A Remington 700 is essentially Remington's budget action. It is push feed. It has their budget style extractor. The bolt stop is a bit hokey and the safety is not exactly a premium design. It is usually finished like the budget action it is. It has a recoil lug that sandwiches between the receiver and barrel rather than an integral lug. It also has bolt on scope mounts that are not necessarily aligned perfectly.
You can remedy some of that by improving a Remington action.
You can remedy a few more things with a custom action.
Last year I bought an American Rifle Company Archimedes action. It's not cheap but it is controlled round feed action with a 3 lug bolt, Mauser like claw extractor, Springfield style ejector, an integral recoil lug, a keyed scope rail, a unique system for primary extraction, dual cocking cams for smoother bolt lift, a floating, interchangeable bolt head for accuracy and the ability to change calibers without an entirely new bolt and it's all finished in very nice black oxide (anodized rail). It is also machined very precisely with toroidal geometry in the bolt lugs to self center and the threads are cut the same every time so that barrel manufacturers can cut drop-in prefit barrels that don't need shoulders turned or short chambers.
That's a pretty big list of things I got for my money. I'm probably missing a few things.
Other custom actions usually have shorter lists. Some have a feature or two that my Archimedes doesn't.
I suggest you make a list of features you want, then look at your options and see if you feel like you are getting your money's worth.
The way I look at it, a custom action pretty much always makes a more desirable rifle. A 700 will kind of disappear in a rack of guns, you have to know what it is to know what it is because 700s are so common. That's worth a little to me.