Check out either XVE or AMP; they are both neat little plugins differing in that AMP has settings for width and height for each of the supported video portals, while XVE allows you to set a unified size for all.
As to the flash block in the WYSIWYG editor, logic dictates you're looking at that dangerous editor after entering the code in the HTML editor, and I'd think both Isptenu and yours truly already warned against that bad habit. So, don't be surprised about the probability of the results. Also: the WYSIWYG editor has had that same issue since at least the WP2.x series. It's not new. And as Isptenu also points out, technically it's TinyMCE that which provides you the optimal rollercoaster experience whenever you mix point-and-click with nitty-gritty (and hardly standards compliant) HTML hard coding.
Which brings yours truly to briefly ponder the significance of your inapposite and broad brushed extrapolation in your parenthetical closing remark, rendering further comment obsolete past a casual observation that WordPress, along with many of its plugins and themes, are but a few examples of a quite selfless and open endeavor, placed in your hands for you to use as you see fit.
For free. By a global community of developers, who deserve a bit more appreciation than inappropriate projections and suppositions can afford.