OK, now you’re talking specifics, which helps in terms of finding solutions. First, the Animation codec is a bit outdated and esoteric, designed for imagery having broad areas of flat color like certain types of 2D cel animation. Since it uses RLE encoding (lossless compression), it’s not that efficient at compressing imagery that has graduated tonalities, which describes the vast majority of 3D animation. h.264 is a very versatile codec standard, but it is not lossless, so “100% quality” will not be possible even at very high bitrates. Video compression, unless designed to be lossless (and h.264 is not) will always result in data loss; the better codecs are designed to make this visually negligible and to give options for trading off file size and playback ease with best possible visual quality.
If you must have very high bitrates for h.264 encoding, I suggest you take look at Handbrake, an Open Source utility that does very good h.264 encoding with many, many options, and can save to a number of different container formats. I’ve only encountered the Animation codec as a Quicktime Pro option, but its limitations make it a second choice (imo) to high-bitrate h.264 despite it using lossless RLE encoding. It was never very good to my imagery when I was using QT Pro years back.
As far as “Why the bitrate cap in Blender?” – it’s been said over and over, there is no definitive answer to that question. It is what it is, so you either live with the cap, or find alternatives like Handbrake. Angsting out over “Why?” does absolutely no good whatsoever. If it’s that big a deal, look into building your own Blender without the cap, or maybe find someone to do that for you. Off-the-shelf Blender is not the only Blender that can be obtained.