I don't think a high yield is noble just because there's a lot, but when they're popping up in big clusters, even poisonous mushrooms are a welcome sight.

Literal

Yield [subject-が] many [just because-からといって] noble [quotative-とは] not-think [but-が], with-a-boom sprouting-[progressive-していると], poisonous-mushroom [even-でも] happy thing [copula-だ].

A mushroom forager's musing. ドカンと is a 擬態語 for something appearing in large quantities or with a dramatic impact. 毒菌 'poisonous mushroom' — 毒 'poison' + 菌 'fungus.' ~からといって 'just because' sets up a concession that's then overridden by emotional honesty: the sheer abundance makes even toxic finds exciting.