Your choice of example is not the best as
(i) negatives usually confuse the issue,
(ii) “hard” can be the converse of “soft” or “easy”.
(iii) Anything can be a pronoun/noun – (a) 2020 Greybeard EL&U “Have you anything that will open this bottle?” or (b) an adverb *2005 A. J. Bruney Microsoft Office Web Components Black Bk. v. 194 The final data need not look anything similar to the original raw data.
So if we consider instead, “I found it difficult.” and avoid, “anything”:
“I found…” is a close synonym of “My experience was…”
“My experience was…” has to be followed by a content clause, which is a particular type of clause, usually considered to be a noun clause, which may have several functions.
(If “My experience was…” is followed directly by an adjective, then the adjective modifies “experience”, whereas with a content clause, the adjective modifies “it” (or whatever the subject is.))
Thus:
“My experience was that it was difficult,” in which “That it was difficult” is the content clause.
“To find” also takes a content clause but, additionally, may also take a reduced content clause. It is reduced to an adjectival complement. “I found that it was difficult”, reduces to “I found it difficult.”
Meaning
The slightly greater formality of the full version [[that...] to be] can create a small, but perceptible, difference between the two:
“I found that it was difficult” – here, the “finding” could be a professional and objective “finding” e.g.
A: Professor, can we have your opinion of question 7 on the examination for 10-year-old students?”
Prof: “I found that it was difficult. It is advanced for young children. It is the sort of question that I would give to 15-year-olds.” (Obviously the professor himself did not find the question difficult.)
And
“I found it difficult.” – Here, it is more likely to be subjective, e.g.
“John did the job in 2 minutes but I found it difficult.”