What does 日曜日のお父さん状態 mean?


This text is from a light novel:

> ラグニールは既に龍王の座を青い龍へと譲り、隠居の身になっていた。
>
>
> ただ、それによって今はどこにも居場所が無いと嘆いており、カガネ曰く「日曜日のお父さん状態」らしい。どういう意味なのか知りたいんだけど、聞かない方がいいような気がした……俺も将来そうなるのだろうか……

I don't understand what 日曜日のお父さん状態 is supposed to mean. I understand the words
for "Sunday", "father", and "state", but I can't figure out what this phrase
is supposed to mean.




日曜日のお父さん状態 is 日曜日のお父さん **の** 状態, or "that status/situation of a dad on
Sundays". の is (intentionally) omitted because the author implies this
expression refers to something every reader knows. See: [-的 adjectives
modifying nouns without な](https://japanese.stackexchange.com/q/21150/5010)

So the sentence says ラグニール is like a typical Sunday dad. What it exactly means
is clearly indicated in the context. 日曜日のお父さん is a metaphor of どこにも居場所が無い
(i.e., "I feel like I don't belong here", "I feel isolated"). Many middle-aged
Japanese businesspersons are so busy and tired that they often have this
feeling on holidays.

