This hits at the whole thing about economic benefit for the arena - we already have that economic benefit of a major event centre in the area. For the past 40 years, about 20,000 people would visit Victoria Park occasionally and spend money on local bars, restaurants. The new arena's economic pitch was always incremental (e.g. get people to spend a bit more money each visit, have a few more events that bring more people down over time than currently).
As you said so yourself - we already have lots of big event traffic and the area remains a dead zone most of the time. That's because big events aren't good at creating a 24/7/365 entertainment district on their own, they are the event equivalent of office-only 9 to 5 sterile office districts. Arena's - shiny new ones or old outdated ones - don't help you solve this meaningfully. We should be critical of claims otherwise.
Similarly there's still no evidence that this $1B+ in public subsidy between the arena and convention centre will result in meaningful development at a scale that would help fill the gaps and start to create that 24/7/365 entertainment district. Unless another development we haven't heard of starts soon, on opening day in 2028 you'll have an attractive, new, modern, sleek - but ultimately similar - situation to today's setup in the area (from an economic development perspective). Therefore, I don't see evidence that much will change regardless of how great this latest design is.