Hi Pascal,
Agree with you that the new version generally looks brighter, and the artwork pops much better. That said I do find the old style less garish, and the iconography for yellow tiles is more intuitive in the original edition. Either way, there is an option to use the artwork of the version you want to see, regardless of the version you are playing.
In terms of gameplay, as far as I can recall, there are just three gameplay changes in the 2019 edition:
1. - Knowledge tile 6 is superpowered, letting you pick up any tile as a free action with two workers or two coins.
2. - Knowledge tile ?15 (3VP per good type sold) is now 2VP
3. - Knowledge tile for 2VP per bonus tile is now 3VP
As a competitive player myself (top 20 on here and #1 on the Digidiced app), I can assure you that for the many reasons outlined in this forum and in those on BGG forums, the new bonus tile number 6 really is so completely overpowered that it dominates the game in the 2019 edition. It means any die can be used for a wild pickup anywhere on the board, for no net loss of workers. With it, you can be more efficient getting what you want, as well as deny your opponent what they want more effectively, every single round. With other yellow tile combos boosting workers/coins received, it becomes even more powerful. The other balance fixes 2 and 3 above are fine. To be honest for me they swing too far the other way, and should have swapped the nerfed tile into the regular stack and put the 3VP/bonus tile into the black market stack, reflecting the fact the animals and other yellows in the black market stack are on average a bit stronger than the regular pile.
I could be mistaken, but I believe Arena is supposed to be a forum for players to play the most competitive version of the game. Knowledge tile 6 skews the 2019 edition and makes it more prone to luck. It makes going first even more powerful. It forces you to try to get ships before your opponent at all costs, cutting down the strategic space to fewer potential winning options. And if you happen to be first player and get bonus tile 6 in phase A, your opponent has no chance at all, providing you are halfway competent. It is so powerful that using it, an average player stands a decent chance against a master, as testified by Pistol Star on here. If you don’t believe the many experienced players telling you so, play enough games of the 2019 edition for yourself, and as a smart and competitive person, you will realise this.
Besides the notorious 6 tile, the only significant difference really is cosmetic. Getting good at either version will make you better at the other. And as I said there is a setting to use the new art in original edition games, if you prefer. I suggest trying that. And if you are determined to throw yourself at the more luck-based 2019 edition, there are many tournaments using it on here that you can try.
I can understand lack of players would be a frustrating issue though. Perhaps this is about turn-based vs real-time? I tend to play turn-based and have no issue finding opponents in arena. Maybe it is something the site admins could look at to see what proportion of games are played in arena/simple, live/turn-based, and across the range of player counts. Then compare to other games and see which arena modes are popular and which aren’t. I’m not sure exactly what you’d do with that data, as some games lend themselves more or less to arena mode, but it could help to inform decisions on arena settings perhaps.