I'm surprised by the backlash in here, to a degree. Do some people actually want to continue with PTCGO forever?
The avatars are jank, without a doubt, but not worse than the current system. They're both pretty awful, but completely ignorable. One is fixable.
HGSS removal? Unfortunate at best, terrible at worst. Will definitely hurt feelings and ruin some collections (rip COL energies). rip my collection of all 2011/2012 max rarity tournament winning decks. It's whatever. Could be even worse if they announce that vivid boxes/sleeves are not transferring. If I had to guess, I'd say they probably aren't, but let's leave that alone for now. This should not be a dealbreaker. If you're playing PTCGO exclusively for Legacy format, then I feel bad for you and you'll have to move to TCGOne. It might not be too late though, we can at least try to give feedback about it, especially considering B&W cards are being included still. On a similar note, I have no idea what's going to happen with my copies Tropical Beach and frankly, if I have to pay the price of losing them (or making them borderline-worthless) to get a client that's not absolute dog, then make it so.
Other than these two things, there's absolutely nothing that should be upsetting about this update. PTCGO has been a terrible 'game' for years and years. It's been a tool, a convenience platform, a stop-gap. People who wanted to 'play the game' kept their own interest by collecting "400 Hatterene V" or the psycho collectors who endeavored to hunt down a tradable copy of every single openable pack, toolkit, tin, theme deck, etc. that was ever in the game. That's not designed gameplay, that's self-imposed achievement hunting. You can do that with any game ever made; try to beat Legend of Zelda with only bombs, get the world record speedrun on Strider. There will be options to do stuff like that on Live too, without a doubt. Losing these things permanently feels bad, but it's an inevitability; this is a platform
The new client is the stepping stone to an actual game platform that can be refined, updated, and polished to meet demands and properly support modern systems and continue to support them moving forward. One minor example that I think is a microcosm of the PTCGO platform, and one that most people just ignore and/or forget is that the PTCGO client literally cannot draw itself in windowed mode accurately to an actual full screen on its own; it always overlaps pixels and has to be moved manually. Problem has existed for as long as the game has had it's own standalone client, but applications have been able to do this functionality properly since Windows 95, natively. There are so many minor architectural flaws with the current client that it would be senseless to continue to support it.
There are tons of features that likely will not be included at launch, but that could be added in the future. Imagine support for old formats dating back to Gen 3. Could definitely be done in generational queues, with all cards being part of the 'battle pass' or an additional DLC. Support for large scale tournaments? Imagine a regional level tournament able to be hosted within the client itself. That could be doable. Support for sealed matchmaking. Support for TWO FACTOR AUTHENTICATION to mitigate the risk of you losing your entire account. Support for a wide array of vanity items and promotional extras more frequently. Aside from the last point, all of these things are an absolute pipe-dream on an antiquated, unsupported platform that doesn't make the company that owns it even a cent of revenue. A platform that directly makes more money has the ability to create jobs to meet demand, and put out more content to continue to meet player desire. If they don't update, they'll be mocked and fade away; similarly to how PTCGO has been for the past few years. Without covid lockdowns, PTCGO would've been the same old often-mocked, often-forgotten, fade-away software that it's been for the past 3+ years.
As far as trading, don't even get me started on how unbearably awful the trading system has become. If you combined the playerbase of 5 years ago + the current feature where the list doesn't reset after accepting a trade, it could pass I think. However, things are way out of control now. There's a database somewhere that is literally screaming and crying 24/7 while PTCGO gets boiled to the brim with dozens of power sellers posting hundreds of trades daily, with more people than ever before looking at them and posting more trades of their own to try to undercut just a little bit to get what they need, while it takes 5+ minutes just to load the list far enough to see the most recent posted listings as to not have to get completely ripped off just to find a single Flaaffy. Come to think of it, it was actually never good at all. It was a janky mess put together that 'worked' to a degree but had such terrible bones it could never be fleshed out to be a fun feature.
If you've played this game for a long time, it sounds like you'll have the world and then some when this new client comes out, and we don't even know everything yet. Be patient and embrace positive proactive changes, even if some of the losses seem heavy now.