Thompson SMGs are iconic American guns, for sure. They almost scream "GANGSTER GUN" for those who associate it with 1930s gangsters, known as the "Chicago Typewriter" and to others, it's venerated for WW2 use, carried by infantry soldiers and marines into battle in real life and in Hollywood movies like "Attack!" and TV shows like "COMBAT!"
It was America's first submachinegun. As such, it was heavy, clunky, and over-engineered. The design of the shoulder stock contributed to "walk-up," and when shouldered, often tended to put the rear sight on the shooter's eyeball.
As an icon, I love it. I grew up watching actor Vic Morrow carry a 1928 Thompson in his COMBAT! role of Sgt. Chip Saunders. Plus, other WW2 movies and shows have portrayed good use of the Tommygun.
But so far as WW2 weapons are concerned, actually I prefer the M-1 Carbine. Lighter, easier to point, firing the more powerful .30 carbine round with greater penetration, I think it was actually better. The best---the Garand. Heavy, yes, but can you say .30-'06?
I do not own one of these neutered semiauto Tommies. Earlier posters explained it very well. If you own one, fine.
A .45ACP longarm can make sense. But NOT at 10+ pounds. In a lighter more M1 carbine-like profile, sounds nice!