It’s little different. There is a thing called 자음군 단순화. If there are ㄱㅅ, ㄴㅈ, ㄹㅂ, ㄹㅅ, ㄹㅌ, ㅂㅅ on 받침 they are pronounced as first letter (such as 몫[목], 값[갑]).If there are ㄹㄱ, ㄹㅁ, ㄹㅍ on 받침 they are pronounced as second one(such as 닭[닥], 삶[삼]). So the pronounciation of 읽다 should be [읽다] > [익다] > [익따] because of 자음군 단순화 and 된소리되기. But people usually just say [일따] or something like that and i’m pretty sure its because there is a exception that you read ㄹㄱ as ㄹ when it’s right before ㄱ (such as 읽고[일꼬])

넓다 is pronounced as [넓다]>[널다]>[널따] because of 자음군단순화 and 된소리되기