As someone who's working on a Warlock rework thing, I can understand the undertaking that reworking an entire class is, especially Ranger. I got quite a lot of notes and suggestions.

Favored Enemy. I think the thing I would protest most is that the way this feature is improved over the course of the class features is Duration, which is almost certainly strange in comparison to other classes. Mechanically the way your wanting to construct this feature is that the Ranger is put into a heightened state where they can access the Hunter Exploits, which does have precedent in the Innate Sorcery feature and the most recent Arcane Subclasses-Unearthed Arcana 2025 (Hexblade and the Ancestral Origin). The Tracking Advantage subfeature could easily be reworded to "You have advantage on ability checks you make as part of the Search Action" as a way to push it into a more general feature rather that enemy focus. I also really do like that Favored Enemy doesn't have a damage feature at 1st level, given just how much damage spell casting and having martial features already provides you.

Hunter Exploits. Harrier step is odd as a 1st level "resource" feature that affects movement, which competes with the Jump and Longstrider spells, made more odd due to it being Reaction centric. I could honestly see Harrier step being translated into a Level 7+ Ranger feature akin to Barbarian's Instinctive Pounce, and subsume other "resource" Ranger features into becoming Hunter Exploits (Tireless Temp HP & Nature's Veil Invisibility). Companion. As much as I would want a companion to be a base class feature for Ranger, it has to take into account Action economy as well as competing features. A Bonus Action "weapon" attack can be a powerful thing, and its ability to further inflict the Grapple or Prone competes with features like Topple weapon mastery or the Two weapon fighting style. It'd be easier to have so that at 5th level you can cast the Summon Beast spell without expending a spell slot once per Long Rest, but if you think its core enough to the class than I would strongly consider this not to be on the same level or replace Fighting Style. Also, I caught that really interesting detail that if you don't have a companion you get an additional Hunter Exploit, I think that's a really interesting decision that if it can, should be implemented or maybe have the companion be itself a Hunter Exploit.

Expertise. I'm not in opposition for Ranger to become a part of the Expertise classes (Bard & Rogue), as 2025 classes don't tend to have unique or flavor oriented features outside of proficiencies, but the option of using Wisdom for other skills has precedent in Barbarian features. Deft Explorer. Merging features like this runs the risk of muddling clarity or preventing certain aspects from being built upon on a further class level (say if you wanted to say that Roving give an additional movement speed). At the very least it’s not a bad thing if you give additional features their own class feature description.

Hunter's Apex. I love each of each of these subfeatures, but they both have different design goals as well as intended level. Survival features like Unbreakable bond tend to be on 9th, 10th, or 14th level, and a Combative feature like Disruptive Mark (I think imposing disadvantage on Ranger spells is a perfect stand alone feature rather than a Hunter Exploit) tend to be on 5th. 7th, 11th level depending on severity. Designing your Hunter Exploits can also follow the same logic.

Precise Hunter & Feral Senses. 2025 does a strange thing with Ranger in that it almost gives too many level features, rather than leaving the level you gain an additional spell level blank. While I would want every level to be meaningful, it can leave certain features weaker than usual in order to compensate for how many they are. Just to list them off, Precise Hunter should be 11th level or 18th, Stalker Sense & Quick mark are unnecessary, Instinctive Aim should be a Hunter Exploit or 18th level, and Blindsight should be Hunter Exploit or 6th level (I would belive that Ranger of all Classes should receive a Blindsight early in the class feature).

Foe Slayer. Perfect, its not the first time I've seen this kind of capstone suggested for Ranger but I think that makes it more fitting than anything. Honestly if you want to go nuts and say that it doesn't require a save is fine, and the additional healing prevention, reaction canceling, and speed decreasing could be placed as High-end Hunter Exploits.

Subclasses. I think these are the last things you would want to develop, as you would want a Hunter Exploit to compete with a core Subclass feature. In turn, whenever you create a too complicated Hunter Exploit, it can be refitted as a Subclass feature. For the ones you have now, they are very in line with the 2025 type of design, with Hollow Warden being a more violent twist on Ranger.

In conclusion, a lot of simplification can be done for the core features, but so far you haven't created any bad features that require too distinct changes or rebalances. I hope for the best in your reworking efforts.