Honestly, the biggest thing wrong with battletech is the same thing that is wrong with anything that has a large group of dedicated fans. That problem is battletech fans themselves. Whether it was bitching about project phoenix, hatred over the Dark Age, or why Katherine Steiner Davion had to wait till she was 108 to get stabbed in the throat, some of the most ardent fans are also some of the most unreasonably demanding.
one need only wander over to the official forums and say "Land Air Mech" and watch the fireworks. Or ask about the Phantom Mech Ability. Heck these days you can even ponder why the home clans would not embrace the Nova CEWS, CLPS, and Null signature systems.
If you want to know how truly bad it can get, one need only look at this example. In 2004 I finally started getting into miniature building and painting. I had a lance that was made of a Berserker (my first Mini ever!) Mad Cat, Enforcer III, and Rifleman. that rifleman was the newest addition and a Project Phoenix Model. I brought it to a random game in St Louis, and put it down on the table. another player asked what mech that was and thought it was really cool. when i said it was a new model rifleman he assumed I was proxying and asked what the mech really was. when I pulled out TRO Project phoenix, he threw the mother of all shit-fits, tossed my book in the trash and broke the miniature, handing me an unseen and telling me he would not let me play unless i used a "REAL" rifleman mini.
does behavior like that welcome new players? does behavior like that put a good face on the larger community? I realize people like this are a minute portion of the larger Mech Head Community, but I still work my tail off every day to make sure these people are mitigated and minimized, so we can welcome as may players as possible.