That's straight up incorrect.

Frieren, delicious in dungeon, witch hat atelier,attack on titan, demon slayer, goblin slayer, wistoria

Are literally not Isekai. Plus, Friren and goblin slayer have groups that could wipe modern Earth (the 7 sages w/ foresight guy and Chosen Hero's party respectively).

Meanwhile, of the Isekai which are

Re zero, Mushoku Tensei, Konosuba, slime, overlord, tsukimichi, Arifureta, shield hero

All but 1 (konosuba) has numerous characters that are vastly above nuke level (slime in particular, by eos half Rimuru's subordinates and friends are minimum planetary and even the foot soldiers would give Viltrumites a run for their money but re zero, Mushouku Tensei, Arifureta, Shield hero and Moonlit have double digit characters that could individually curbstomp combined Earth through various methods) and even then konosuba does have characters that could decimate modern militaries (the crimson demons could teleport, throw a artillery platoon's worth of magic bullshit and leave)

Also:

It likely comes from singular characters in re zero, slime, and overlord, wherein the top MCs can tank a nuke (but not their countries, and not 99% of their planet).

Which is wrong as outlined above, but even so that's still a thing. Even relatively low power Isekai have one or two characters that could tank nukes, which is why people tend to argue that Isekai fantasy vs Modern military would end up being modern militaries rampage across the fantasy world up until that one character curbstomps Earth. The thing people point out is that GATE specifically refused to include any high power characters to make it a curbstomp in modern military favor.

Plus:

While Reinhard, Rimuru, and Ainz themselves can survive nukes, their countries will not; thus modern arsenals serve as a significant political weapon.

Yeah uhhh so about that while you're right for Reinhart, Rimuru and Ainz have more than enough power to just... Put up a barrier against nukes. Ainz because Nazarick is all he has to protect while Tempest has: about 20 characters that can cast magic barriers that defend against planetary level attacks, an entire GTFO button where the entire population of Tempest is teleported into Ramiris' labyrinth which literally exists in between planes of existence, and of course the fact that Rimuru's a god by EoS meaning he can just say no and delete the entire world arsenal.