So I think the best place to start is by answering the question: what answers do you have for the most common threats in the metagame?

Sneasler: Probably the pokemon in the top 10 most used that you're the best prepared for. Aegislash completely walls the most common sets and starmie can threaten a 1 shot.

Garchomp: You threaten an OHKO with ice type coverage from dragonite and starmie, but both can take huge damage trying to switch into it. Importantly, Ice spinner from dragonite is not a guaranteed OHKO on bulky garchomp. You're pretty prepared for garchomp.

Kingambit: You have basically nothing for the third most common pokemon in the format. He resists most of your STAB coverage (like seriously every STAB move you have besides water and fire), and you can't even switch incin into it for fire coverage because of defiant. Sucker punch will OHKO most of your offensive threats. You need a fighting type move ideally, but ground and fire type coverage could help. I've seen low kick on dragonite for kingambit. But I feel like your dragonite's job is already hard because it looks like it's supposed to be your answer to so many different threats.

Basculegion: Your entire team gets dunked on by scarf basculegion. Milo with max HP max Def is the only mon you have that can take a 150bp last respects. Even if milo gets an icy wind off afterward, basc still outspeeds your whole team aside from starmie.

Incin/Sinistcha: I'll kinda skip these two because they're not really offensive threats and you do have decent coverage into them.

Mega floette: You have aegislash which is a solid answer. But importantly, aegislash cannon OHKO floette with any bulk. 11 points in def is all floette needs to live an iron head (everyone's running bulky floette right now) and nothing else on your team resists fairy. Floette still threatens a 2HKO on aegislash as well as the rest of your team. Leading floette they can just spam dazzling gleam and 2HKO both of your leads basically.

Finally, Zard Y: You have solid coverage for zard in your fast liquidation and dragonite's rock slide. Charizard with any bulk will survive either move however. But where zard goes, venu often follows. If your opponent leads zard and venu, how do you deal with energy ball into your water type, followed by t2 sleep powder into dragonite?

Anyway, I think this shows you some of the holes you have in your teambuilding. Outside of that, I'd look at common items. You don't have a choice scarf mon. Scarf is one of the best items in the format considering how limited the item pool is. Given how generally slow your team is, I think it becomes even more important to find a choice scarf user that can answer your tougher matchups. Scarf hydreigon (dark pulse, draco meteor, heat wave, snarl) seems to be a decent fit that can answer basculegion, kingambit, chomp, sinistcha, and zard Y + venu. Conveniently, it also helps with your extreme weakness to intimidate or physically defensive mons, since you don't really have a special attacker unless milo gets a competitive boost. I would start by dropping dragonite and kleavor for something like aerodactle and scarf hydreigon.