简化句子：It is only my shoes that are dirty.

简化句子：It is only my shoes that are dirty.
简化句子：It is only my shoes that are dirty.

简化句子：It is only my shoes that are dirty.
Only my shoes are dirty.
分析：
这是句强调句,简化的当然只有强调部分了
强调部分是主语only my shoes ,强调句格式It is +（强调部分）+ that ……（从句）
如果仍有不懂的可以继续追问我

only my shoes are dirty.

my shoes are dirty.

only my shoes are dirty. It is ...that...是强调句式

my shoes are dirty.

only my shoes are dirty.

only my shoes are dirty

这句话为一句强调句式。即it is…that，强调只有我的鞋，这双鞋怎么样了，这双鞋脏了。
（规律）一般强调句变简单句，只需要将强调句式省略掉就可以了，省略不影响句意，结构也是正确的。
所以这句话的简单句就是only my shoes are dirty.

Only my shoes are dirty.

强调句型，it is 。。。。that 直接去掉 only my shoes are dirty