Hitting the gym to become a swoletariat, looking to arm myself as well.
I've gone shooting before, and my Dad just bought a couple guns himself because of all the pogroms he's been seeing against Muslims in ingerland.
I'm based in the United States of Amerikkka, mods please let me know if this isn't allowed!
I think a semi-auto shotgun is probably as good as a rifle within the scope of defending yourself inside your home. At home defense ranges, a regular shotgun bead is plenty to hit a man sized target reliably every time - you can hit clays moving way faster than a human with them just fine.
Higher risk of overpenetration (00 shoots 9mm pellets, which retain a lot more energy through walls than lightweight 556 does), higher risk of failing to cycle (recoil powered shotguns need to be tuned right, gas powered ones are spendy), and you definitely should not shoot without properly aiming in any situation, that'd be massively irresponsible.
It can work, but it has disadvantages that a rifle does not, and no real benefits over one.
Fast shooting with a bead certainly is properly aiming, it's just doing it fast. Penetration is question of ammunition choice - there's more options than 00, but that's just to say you have options and need to make a judicious choice - I don't care to get into an ammunition discussion. I think the price of a decent semi-auto is really the strongest argument against one as compared to a rifle.