Based on player ID numbers, the EN PC/PS2 servers of PSU didn't go much higher than a total of 50k players in its lifetime
I remember (though the forums are so dead I couldn't even find them on Wayback Machine) that there were around 30k Network Mode accounts reported on that server by the same metric after the first week. That was just NA players (the European and Australian release date was a calendar month later and only a handful of us imported the game, so a sizeable portion of the remaining 20k were probably launch players from the second-class regions.
It goes to show how important a good launch was at the time, but I feel that was a different age and that new or returning players can happen longer after release now we're not dependent on new players noticing the game on shop shelves. So while the NGS launch may be disappointing in terms of player retention, I'd say it's more of a salvageable situation than 15 years ago.
I doubt that any of the PSO1 versions had thousands of concurrent players at any time either.
I quoted 26k from an interview with a first-hand source I think in the other topic. I suspect that was the highest PSO1 ever reached.
If PSU would be remastered as a full Online Game like PSO2 with some changes so that the multiplayer is needed and rewarded those 250k would be broken on day one in just 1 hour.
This is at worst amusingly assumptive that people would want to go back to many of the issues Universe had, on the level an unfair comparison since you'd be comparing post-development Universe with the Network Mode that launched in 2006 which iirc had like four quests between the GUARDIANS Colony and Parum, and at best a vague non-statement of "if you make it better it'd do better" which also applies to everything ever.