(this isn't necessarily an answer but it's too big for a comment, IMO)
When I first started using Eagle, I quickly came to the conclusion that the libraries are old and not reliable. I took a good chunk of time and revamped a lot of what I cared about most.. which is basic resistors and capacitors. Creating the parts is easy... most of the work you need to do is in creating accurate packages and attributing parts properly. Here is my secret weapon, though:
Mentor Graphic's LP Wizard
This bad boy has saved me so much damn time drawing accurate packages for basic SMD footprints. Here's the skinny on why I love this tool so much:
The footprints it gives you are based on IPC-7351 or the appropriate JEDEC standard
While going with a manufacturer's recommended SMD land pattern is usually preferable in my eyes, for things like passive SMDs, this is great because it's a source of truth. If I want to create packages for 0402 through 1206, and I use this tool for all the dimensions, I know I'm going to have consistent scaling of things like pad spacing, courtyards, etc. One part won't have drastically different features and come out looking weird on the actual board. Anyone who has ever taken a look at the stock Eagle libraries can attest that there isn't much consistency. Using the tool, which in turn is based on these standards, is a great way to build a standardized library of parts.
For basic footprints, you get different sizing versions to tweak for space/reliability
I believe this is inherent to the standard, but for basic passive SMD footprints like your 0402, 0603, 0805, etc, LP Wizard will give you the option to switch between Least, Nominal and Most versions. These tweak the actual pad sizing to yield you a smaller package or a bigger package. A bigger package might be preferable to ensure bigger solder fillets for increased reliability while smaller pads might be better for creating a super dense board. Either way, these are footprints that have been tested and agreed upon to serve well in their intended application. To me, that's a big time saver and awesome.
Mothertruckin' CAD export
Take advantage of the 10-day trial of this tool for this one reason. CAD export. LP Wizard will export packages to an Eagle script that you can run inside your library to generate the packages for you... complete with part markings, courtyards, etc. This is GREAT for importing a ton of stuff and then being able to go and tweak it on your own. Usually, I'm sitting there with the calculator app open doing all the dimension math to build my mirrored land pattern parts and what not but the CAD exports takes from you nothing to something good in no time flat.
You're still going to need to invest time to build up a reliable parts library, but there are definitely ways to increase your productivity, and to me... using something like LP Wizard is one of those things.