With the removal of Mega Evolution it seems at first that Charizard would get demoted back to a lower tier weather abuser, but Gen 8 did toss him a couple bones, even if they don't really make up for the loss of his Mega forms.
The first of these is a new Gigantomax form. While it looks impressive and it's used by Sw/Sh's champion, it's no Mega Form, as its stats are all the same save for the doubled HP. It is, however, arguably one of the better G-Max forms, as its new G-Max move is essentially a stronger version of its already potentially souped up Fire moves that inflicts a rather devastating damage-over-time effect for 4 turns, chipping away a noticeable 1/6th of the opponent's maximum HP per turn. If I recall correctly, this effect is also applied to the opponent's side of the field rather to the opponent specifically, meaning if they switch out, the Pokemon who comes in will take damage instead of the effect dissipating entirely.
The other thing Charizard gains is Heavy-Duty Boots, an item practically designed for Pokemon like him. As long as he can avoid Knock Offs, he no longer has to worry about his crippling 4x Stealth Rock weakness. It does mean giving up a boosting item like Life Orb or Choice Specs, however.
Charizard @ Heavy-Duty Boots
Timid - Solar Power
252 Sp. Atk, 252 Speed, 4 Sp. Def
-Fire Blast / Flamethrower
-Solar Beam
-Focus Blast / Scorching Sands
-Roost
This Charizard is heavily reliant on Sun support, at least in the higher tiers where he needs to justify using him over other Fire types. However, thanks to Solar Power, this Charizard set actually outdamages Mega Charizard Y in the sun.
252 SpA Charizard-Mega-Y Flamethrower vs. 0 HP / 0 SpD Mew in Sun: 256-303 (75 - 88.8%) -- guaranteed 2HKO
252 SpA Solar Power Charizard Flamethrower vs. 0 HP / 0 SpD Mew in Sun: 294-346 (86.2 - 101.4%) -- 12.5% chance to OHKO
The drawbacks, of course, being that he doesn't automatically summon Sunshine, and he lacks the significant Sp. Def boost that Mega Charizard Y gained.
Fire Blast or Flamethrower are your main STAB. You don't really need Air Slash or another Flying STAB; there isn't a whole lot that it actually hits that isn't already getting obliterated by a Sun-boosted Fire STAB. Solar Beam blasts through Water, Rock, and bulky Ground types and in general gets good coverage with his Fire STAB. Focus Blast nails Tyranitar, who is otherwise a bit of a problem for Charizard as it overwrites the Sun with Sandstorm, neutering Charizard's Fire moves and Solar Beam. Focus Blast blows it away, along with Heatran, who also takes pittance from those moves. Scorching Sands is a more accurate way to deal with Heatran and at least deters Tyranitar, but doesn't flat out KO it like Focus Blast can do. Finally Roost lets you take advantage of switches you force to heal off Solar Power damage as well as any other chip you might have taken in the process.
Forgoing Heavy-Duty Boots and packing a Life Orb or even Choice Specs instead can be an option, turning Charizard into even more of a devastating wallbreaker, but aggressive hazard control becomes mandatory in such a situation. With a Choice Specs equipped, however, he does have a fairly good chance to 2HKO Chansey with Sun-boosted Fire Blasts, so if you want obscene amounts of power at the cost of longevity and ease of use, it might be something to try on your next Sun team. Charizard can be a monstrous wallbreaker that slower teams can really struggle to deal with, and I think he gets a bit overlooked by the competitive community. I'm not saying he's fantastic, but he definitely has a valid niche in my opinion as a wallbreaker on Sun teams, even without his Mega forms.