Then, in response to the the bolded sections: When have you seen a Fighter completely trivialize an encounter? A Rogue? A Ranger? When have you seen any martial class shut down an encounter the way a Wizard (or any spellcaster really) can?
Fighter - Trip attack on a flying dragon making him plummet to the earth and die.
Action Surge to kill a near dead boss before he goes or gets another legendary many times.
Final example (and this admittedly required a feat and a magic item)- While wearing a Ring of Feather Fall, Misty stepped (using Fey touced) into the air above a Giant vulture with a cultist rider. Threw a net on that vulture which then plummeted to the ground along with its rider.
Rogue - First example is Mage Hand Legerdemain to steal enemies weapons and occasionally a spell focus. Combined it with disarm from the DMG quite a bit if the person was holding the item and it was not being warn.
Also had a Half Elf Rogue that had expertise in 7 different skills and proficiency in another 5. He completely trivialized all the wilderness/navigation stuff because he automatically made the all the checks from 3rd level on (expertise in both Survival and Nature). Also never missed an investigation check or a charisma check (expertise in Deception, Investigation and Persuasion). It actually caused a rub because with a 14 wisdom and charisma he was substantially better at charisma checks and survival checks than the Warlock and Ranger respectively who expected to be the best at those checks. I will also add though he was a glass cannon with a 10 constitution, and while he did ok damage with sneak attack he was hands down the weakest party member in combat.
Ranger - Goblin Fey Wanderer using (abusing) concentration-free Summon Fey (Mirthful) and Beguiling Twist just completely dominated the "difficult" encounters. If you want to talk about OP spells, that is about the most OP I have seen in tier 3. You are throwing outmultiple 1-round Charm Monster equivalents over and over every round with your Feys are getting attacks (and you after the 2nd round) are then you are twisting a save if someone makes it. The combination of multiple pets on the battlefield controling space, multiple attacks and multiple bonus action charms, every single round and then thrwoing frigthened anytime someone saves makes it the best controller I have seen in play through tier 3.
Another example from the same Goblin, a Foolish DM tried to have a Dragon use Frightful presence on us. Twisted the Frightened back on him. Then the party pelted him from range until he died.
Third example - Ensnaring strike to make a flying Chimera plummet to the earth where he was heavily damaged from the fall and then hacked to death by melee martials.
Yes, Wizards have weak spots, especially in 5e where they have taken good measures to nerf that class down to more acceptable levels, but any smart wizard player will have taken measures to either mitigate those weak spots or remove them entirely.
Sure, at a price though.
Also, no Wizard is giving up anything for getting Counterspell, it is a serious contender for "best spell in the game" specifically because it can shut down other spellcasters. And if something needs something that heavy handed in order to bring it down a peg or two, then there is something seriously wrong.
It depends on the game. If you are playing enemies casting spells and they are doing it in situations where a Wizard can get within 60 feet without using other reactions, then yeah sure. But that is situational. In those situations it is king. However, if you have counterspell prepared a lot of nights you will go to sleep without using it. Fear on the other hand is almost always useful, so you are giving up on the power of CS to be less situational.
I will also add that an Arcane Trickster can be almost as good at shutting down casters by taking either their component pouch or their focus and doing on a bonus action without using a spell slot.
