As an argument, it is terrific.
It never explains why permanent parties are better, although the text is structured this way. I had to disassemble in five arguments to understand. Only at the bottom part it address the topic at hand.
I feel you are dissatisfied with parties in general, but please try to keep on topic
Off Topic Arguments
1. You say it's bad without saying exactly what's bad and why it's bad. You're just issuing your opinion, which is perfectly valid, but if it was supposed to be an argument, you may want to rewrite.
2. "None could be created for exp share with alts" is multiboxing rule, way beyond the scope of this thread.
3. No player loses experience and there's a small % bonus for exp sharing iirc to address rounding. There's no change to multiple attackers bonus. As the name suggests, it shares the experience, so it is evenly distributed among everyone fighting regardless of their role in the fight. Otherwise, only players with combat role (fighters / MVP) gain experience.
Share is the traditional solution to support roles, and usually easier to balance: Just compare healing experience versus monster experience.
Anyway, the argument isn't "all players lose", but "MVP lose" and "players in combat roles will gain experience evenly instead of proportionally to damage dealt".
That is valid argument, after all. Even shares or proportional shares, what's more fair? As if I knew! That's, however, is also totally out of scope of this thread.
On Topic Arguments
4. You claim about Illia is, obviously, valid. You can always handle raid parties externally, like Illia does, instead of using party system. That's a valid argument and on topic, hooray!
5. Using alts to keep the party when switching is also an on topic argument, and a proposal for an hybrid system where both ephemeral and permanent parties exist.
Which is interesting, there's no "hybrid" option on the poll, it's worth noting and discussing and perfectly on topic. Although personally I think players will do whatever they want as usual, just like there are guild butterflies (change guilds twice a week) and even marriage had people who would divorce the same week again... And again... And again.......
So while you use party in an hybrid manner, you probably should vote on the main, ideal, or how devs should treat parties. Which, in your case, is permanent
PS. Just as I express my opinions freely even about other people opinion, feel free to do the same and do not keep resentment. Let's try to avoid personal attacks, but arguments are arguments.