誕生パーティーに行けたらいいのに vs 誕生パーティーに行ったらいいのに

Question

誕生パーティーに行けたらいいのに

vs

誕生パーティーに行ったらいいのに

Is explained as

1. I wish I could go to the party.

2. I wish someone would go to the birthday party / You should go to the party. (suggestion to other people.)

I'm having a hard time grasping why the second one couldn't also be if i went to the party it would be good?

I can't seem to figure it out...

Any help would be appreciated!

P.S

I've seen these sentences:

JLPTの１級に受かったらいいのに。 I wish I could pass JLPT Level 1.

明日、お天気だったらいいね Hope the weather is nice tomorrow.

But they are still using the たらいい, which furthers my confusion

Answer 1

たら has three meangs. One is "if". For example, 誕生パーティーに行けたらいいのに means "If I could go the party, it would be good". that is "I wish I could go to the party"

Another is "when ～, and then". For example, 昨日、学校から帰ったら、家に親戚のおじさんが来ていた(When I came home from school yesterday, my uncle stayed at my house.).

The other is "Why don't you do something?". For example, 英会話の学校に行ったら(Why don't you go to an English school?). たら in 誕生パーティーに行ったらいいのに is this usage.

Answer 2

I think the main thing is that it'd be weird to suggest to yourself to do a volitional action like 行く, so the natural subject would be someone else. The other examples don't really have any volition in them, which is why they can be easily understood to be oneself. However, I think you could make the original sentence if you explicitly made yourself into the subject.

私が誕生パーティーに行ったらいいのに