Dolphin is quite good as far as SEO is concerned and may easily be adapted to your specific needs.

Dolphin URLs are simple and readable - trust me that /m/ in the URL makes absolutely no difference. Absolutely every public page in Dolphin is easy for SEs to crawl and is linked through a configurable menu that you can control 100%. Also, profiles and blocks that you can add via Builders can create even better cross-linking within the site to make sure all important pages are crawled often.

Now, see more with META tags - those are somewhat less important these days, but are still considered as meat and bone of SEO. They are not. Anyway, there's no hard-rule for creating meta-tags for crowd-sourced site. Unless you feel like going to even page and adding custom tags manually - there's no benefit from "generating" meta tags from the content - SEs do it all by themselves.

What REALLY matters is making sure you've picked a niche of the right size and information on your site is relevant to it.

With that said, we will still look at what can be done in terms of improving Dolphin SEO. Perhaps a 7.0.9.SEO edition is in order. Specific suggestions, anyone?