Favored Enemy and Natural Explorer, I'll give you. The others aren't insignificant, especially the ASI and Defensive Tactics. Or Iron Will. Or Ethereal Step.
Defensive tactics is OK but it's easily at least matched by [+1 AC from Fighting style, the odd parry or riposte from Battlemaster, and 3 x short rest bonus action heals from Second wind).
The ASI is at least matched by Action surge. If the latter was available as a feat, I take it every time.
The 1 extra 2nd level spell per long rest, is easily matched or beaten by a few Superiority dice per short rest.
Favored enemy and Natural explorer improvements you wouldnt miss if you didnt get them, and you'll probably never even use them. Id rather a single skill proficiency (even one chosen at random) over those abilities.
The skills are nice but hardly groundbreaking. Skirmish is situational at best. The only amazing thing you really gained was Cunning Action.
Expertise in Perception (and Stealth) is amazing. +2d6 sneak attack every single round is amazing. Hide at will for advantage every round is amazing (you also have pass without trace as a ranger dont forget so with expertise and a Dex of 16, you're hiding at around what... +25 to Stealth!).
I take that over an extra 3 hit points, an extra 2nd level slot per long rest, +1 ASI, 2 extra 2nd level spells known, an average defensive ability (that I probably wont use that much due to being ranged) and some useless exporation stuff (that I can work around anyway with Expertise in Perception, Nature, Stealth and Survivial!).
And then the very next level the straight Ranger gets Conjure Animals 2x/day.
Each time he casts it, his Hunters Mark drops (the main source of his damage).
The Fighter or Rogue get an ASI instead. If I had to choose (again) between 2 x Conjure animals of 3rd level per long Rest, or an ASI, I take the ASI.
You're not a half baked summoner; you're an archer (ranged damage dealer) and scout.
OK, Ranger levels 6-15:
6) I'll give you this one sucks. Favored Enemy, Natural Explorer, never have never will defend those features as they are.
7) Archetype feature. Defensive Tactics, Iron Will, Ethereal Step, all solid and useful. Also an extra 2nd-level spell slot, means an extra casting of something like Healing Spirit, Pass Without Trace, Silence, Spike Growth, Lesser Restoration. Good level.
8) ASI/feat. Obviously a good level.
9) 3rd-level spells. Which means Conjure Animals. Great level. Gloom Stalkers get Fear, awesome AoE control. Horizon Walkers get Haste.
10) Hide in Plain Sight and Natural Explorer III. Yup, this is a bad level.
11) Archetype feature, usually a major offensive boost. Multiattack, Stalker's Flurry, Distant Strike, all of them pretty good. Also another 3rd-level spell slot.
12) ASI/feat. Obviously good.
13) 4th-level spells. Guardian of Nature for all the advantage I want in one battle. Or Conjure Woodland Beings. All good.
14) Favored Enemy III and Vanish. I'll call this a mediocre level, rather than straight bad. Yes, Vanish is a gimped Cunning Action 12 levels later than the Rogue, but bonus-action hiding will never not be useful especially for archers.
15) Archetype feature. Most of them here are OK, not great but not bad. Average. Also an extra 4th-level slot, which is better.
Now pick virtually any other class in the Book (with archetype).
I bet you what
they get as class features from levels 6-15 are much (much) better than that list.
All the full casters smoke it. Paladin smokes it. Monk, Rogue, Warlock smoke it. Id literally take 10 levels of Battlemaster Fighter over Ranger 6-10 and be happy (and be one level away from my 3rd attack per round) or take 10 levels of Scout Rogue over those levels of Ranger (and be 1 level away from reliable talent).
Seriously, the only way that list looks even close to OK is if you use Xanathars subclasses to add extra spells known (and the better spells from that book), and the pretty sick class features of the Gloomstalker and the Monster Slayer.
You still have to wade through a lot of trash to get those good abilities though, and Gloomstalker is pretty front loaded also (and screaming to be combined with Assasin).
Monster Slayer is the only Ranger archetype that is worth hanging to later levels, and dealing with trash levels, for its features.
Even then, when I hit Monster Slayer 15, Im likely taking the remaining 5 levels in another class (Fighter and Rogue in some combination).
The Ranger capstone is so bad that I'd rather take Rogue and/ or Fighter levles to round out my skills and fighting abilities.
About the only thing I would miss would be Steel Wind strike for a reasonable AoE, and maybe Swift Quiver (but between sneak attack and action surge, and saving concentration for Hunters Mark, and saving my bonus action each round for cunning action +advantage from hiding, I could made do!).