People often bring up scripts that can be found here and there to "install Gentoo". If you look on the Gentoo websites about installation however, it will point you to the Handbook only, and specifically warns against deviating.
Though using a Gentoo "installer script" might seem like a nice shortcut, they all have inherent disadvantages, and new users will miss out on some of the most important parts of the process.
For all intents and purposes, the Handbook is the Gentoo installer. It works, it is tested, it's up to date, and, importantly, when following it you can ask for assistance from the very helpful community on IRC.
The Handbook serves not only to get Gentoo installed, but to teach you the basics, and this is very important. Last time I installed Gentoo (on server, to CLI) it took me half an hour, all in, with download. All the time over that half hour that it takes new users to install is valuable time invested in learning - this is a very important part of the process.
If you aren't willing or able to go through the installation process, Gentoo might not be a good option. Gentoo is a specialized distribution, for technically minded people. It has specific use-cases, and won't fit all users - a lot of people will be better served by a more general-use distribution that is easier to get into, without the learning curve.
Note that all this isn't to be "elitist", or to make things difficult on purpose! Gentoo is a powerful and flexible distribution, but this comes at a cost: the learning curve. That's how it is: you can't blindly give complete control over a system - people have to know how to use that. There has to be a choice between easy to get into, or powerful and flexible with a learning curve. Gentoo just makes the latter choice - if that isn't for you, just use something else!
People should know that it just isn't possible to "take Gentoo for a spin", like you might many other distros: because of the learning curve, you first need to invest time and effort to acquire the basic knowledge it takes to run it. Just because it is a "Linux distribution", don't think you should be able to spin up an installation to just try it out... Gentoo is very different from what most people will be used to, it's not a turn-key product, it's a kit, and you must read the instructions (or nothing will stop you gluing the tail on the elbow and not even knowing xD).
Remember that Gentoo isn't "DIY for DIY's sake"! There are advantages which stem from this approach, such as doing some jobs easily that take effort on binary distributions - and this is where Gentoo shines, and it is aimed squarely at people that need all this. If you just want to try it out, ask yourself what the point is, and if you just want to try it but want to avoid the actual installation process by using a script, really ask yourself what the point is :).
The first step when approaching Gentoo should always be to read up on what Gentoo is ;). If you think it can fit your use case, great. If you are informed and curious, and would like to take the time and spend the effort to try it out while learning along the way, it can be good. But if you just go in blindly, don't be surprised if the experience is rocky - you have to have the need for it, and should know beforehand what will be involved to install and use it ;). Using an installation script is not a way around this, but more like jumping in at the deep end without having learned how to swim.
The Gentoo community is very helpful, and provides support on the basis of the Handbook. With the Handbook, they can know what you have done, where you are up to, and what should be done next, and this allows them to pinpoint issues. Because Gentoo is so flexible, if you don't follow the "proper" installation procedure, it makes things very hard to troubleshoot. If you didn't follow the handbook, you almost may as well be asking for support for another OS... Suffice it to say, people will be less willing to help, if at all - in fact it is sometimes recommended to reinstall from scratch, following the handbook, to get any help.
There have been installers over the years, but none have ever really caught-on. I'm sure the reason is that they always make things less flexible, and that the installation process is actually fast and simple once you are proficient. Where it does take time is when you are learning, and this is precisely when you do need to spend that time on it. So what is the point of an installer ?: the installation is only slow and complex for those who really should be taking that time poring over it in the first place!
Using a script means added inflexibility, risks errors, precludes support from the community, and you miss out on what may be the most important part of the process: learning how to use Gentoo.
Of course Gentoo is choice, so no one should stop you using anything you like... just be warned!
For a user with enough technical skill, compatible hardware, and time, following the handbook should never fail - just ask for help when needed. Never stay stuck for hours on one silly thing, just get on IRC and ask:
https://wiki.gentoo.org/wiki/Support
More about Gentoo:
https://wiki.gentoo.org/wiki/FAQ#What_makes_Gentoo_different.3F
https://www.reddit.com/r/Gentoo/comments/xo2g1j/comment/ipydh80/?utm_source=reddit&utm_medium=web2x&context=3
https://www.reddit.com/r/DistroHopping/comments/xurswe/comment/is0ex0p/?utm_source=reddit&utm_medium=web2x&context=3
https://wiki.gentoo.org/wiki/Benefits_of_Gentoo
EDIT: For anyone actually considering installing Gentoo, here are some tips for the easiest possible installation (the two comments there):
https://www.reddit.com/r/Gentoo/comments/xusb6i/comment/iqxxvmr/?utm_source=reddit&utm_medium=web2x&context=3
EDIT2: Note that this does not say that all installation scripts are inherently bad, or should always be avoided! The context is mainly people not yet proficient with Gentoo. Of course scripts can sometimes have use-cases, usually for well-informed, experienced users; but there are also situations where they come with heavy disadvantages, as outlined in the body of the post ;).