There is a comprimise. But it may change the way you think about designing sites as well as coding them.
It is quite possible to use a subset of most of the "new" technologies that either:
A second example of number one is a technology that works "in some fashion or other" in all browsers. I will caveat and mention that I mean all 4.* and higher browsers, but I can explain how it will do no damage to earlier browsers that do not support it. What I am referring to is a subset of CSS. All 4th gen and higher browsers support some subset of CSS -- wether they agree on how to render it is another matter. But this brings me to my next point.
If you're coding for a large audience that uses such a wide variety of browsers, you should stop caring if your site looks 100% the same in every browser. It won't happen. Not in any practical way. And trying for 100% similarity becomes a maintinence nightmare. If one small change needs to be made to a page, you then have to re-check in every browser -- and probably make small changes for every browser's sake.
So if you take the plunge and commit to the philosophy that it's "ok" to have your sites look a bit different from browser to browser, there are a couple steps you can take to make your transition a success:
So you can code to modern web standards without throwing out older browsers. You may not get to use all the toys in your toolbox, but it does not mean that you need to wallow in 5000 nested tables.