I can see both sides of the argument personally, and accept the justification offered each way. I also don't like to personally criticise how another club has chosen to build their track too much.
I have yet to see a club that has raised the bar like this, suffer in new membership and have increased injury rates. But what I have seen, is a lot of older riders choose not to ride these newer more technical tracks. I don't like them either, and have considered not riding some but I like a challenge myself, so I tend to suck it up and get out there even if I do come last, and keep my thoughts to myself.
I guess the increased injury rates will come from riders trying to go fast on a track when they have not built the skill the track requires. This wont be at a club level I don't reckon. I don't see any problems in club membership both new and existing either, rather there may be less nominations the from older riders on open days or series rounds because of people who don't want to get beaten on a more technical track.
Don't get me wrong, I like more traditional flowing tracks as well. I also think that clubs need to ensure there is enough of the track for new riders to learn basic skills on. Grafton recently just got rid of their pro straight, which polarised the club a bit, but the result was great. The track has something for everyone. Hawkesbury have a brilliant take on it, with a "Kids straight" to give new riders what they need. Beenleigh and Pine rivers have both pushed boundaries in their own directions, but they still have nothing on Sleeman. Nerang still has a formidable first jump for many riders, but thats not unique either, Maitland has one just like it. Lets not mention Hinterlands Mammoth sprocket destroying start hill, or Woodonga's flat first corner.
Im just trying to point out that variety is a good thing in BMX, so is clubs pushing boundaries. Too much of the same thing does no-one any favours, hence my take on it. If you are worried about all clubs turning into mini Sx tracks, I don't think that will happen any time soon. There is still to many people on both sides of the fence.