I've had a look at the AS rules and I can't imagine what people were upset about. it looks fine. it looks like a streamlined version of battleforce made to cater to miniatures gamers. CBT breaks down with too many units per side and just becomes a slog, so I'm actually looking forward to getting some AS on the table once I have 2 companies painted (should just be a few weeks at this rate).
I'll speak only for myself but i dislike Alpha Strike's lack of detail. It makes many 'Mechs completely indistinguishable beyond looks. (To be sure, standard BattleTech does have some duplicate units but these are far rarer than in AS). Shooting becomes a bit too uninteresting "check if you get to apply a damage value to the enemy" in a game with variety of different weapons. Stuff like falling down vanish completely from the system. As i said, it is not simulationist anymore. BattleTech is semi-RPG as it is. It is fun to see how a battle evolves depending on if pilots can keep their 'Mechs under control or not, if they can hit their targets at critical times or not.
Sure, Alpha Strike retains some of that but less, and that is the big deal for me.
I do wish the standard BT system was faster to play though. It is unnecessarily cumbersome at times, and there's a bit too much randomness in the wrong way (and it doesn't help called shots and the like tend to be prohibitively difficult to use as probabilities go).
It does get slow when you start adding more units, for sure. This is a good thing about Alpha Strike, it allows company sized games in reasonable times.
I'll never understand edition wars nonsense. For months I've been reading whingeing nonsense from 30k players about how they didn't want 30k to go to 8th edition and how 7th edition was perfect and now that it's been announced that 30k is staying in 7th for the foreseeable future people are crying about that. CBT isn't going anywhere, so why anyone should get upset that a different version of the game is being supported is just beyond me.
A problem with multiple editions existing concurrently is that the older one will likely lose support sooner or later. And that bothers people, probably. Not to mention, losing out on good updates on rules. I'm not a Warhammer 40k player but i can see it being annoying switching between rulesets just to use different eras of play if both are still considered valid rules.
This assuming there is implied or stated support for the old edition. If the other game/system gets discontinued, then... well, that happens. Old system can be still played.
With new editions, the worst case is when important old stuff becomes unusable, namely miniatures; rules are a natural casualty.
The idea of existing rules being
perfect is nonsense nearly always. That's just fanboy talk. And people also complain when something is too similar to the old ("the perfect one"), or whatever else.
New editions may make too radical changes or miss the point of some existing systems though. Consider DnD 4ed and how it lost some freedom compared to 3.5ed, cookie cutter builds and whatever else. Though i believe 4ed did have some good ideas too.
And that's why Catalyst would have to piss of the fans if they went with a modern style of mech designs. They either don't change and turn off new players/fans, or make changes and piss off their dwindling veteran player base.
Modern-style and modern-art are different things. The new art for the old unseens have gotten quite positive reception. They have modern art, with some change but they capture the spirit of the unseen. I don't think they'd get a negative reception from potential new players (once they get minis anyway, and presumably a new Introductory Box Set with them).
A lot of BT 'Mechs could use a new art pass and minis, certainly. Though when it comes to minis, most of the terrible ones seem to be from post-Clan Invasion Technical Readouts, not the oldest ones. Most of 3039-era 'Mechs look just fine in plastic and metal but some later FASA-era ones are really mind-boggling, both their art and minis. Modern CGL minis and art are good for most part.