That’s debatable. The Art line is really good from a technical perspective, but some people feel they don’t have “soul.” I think a bigger problem is that they have no concern for weight. For instance, their 105mm 1.4 is over 3 and a half pounds, and Nikons equivalent lens is a a little over 2 pounds.

That might not seem like a big deal but it certainly is when it’s hanging off of you for a full 12 hour wedding.

That said I still have a Sigma 35mm and 20mm in my kit.

Depends on how you define "best". Sigma has improved a lot in recent years and is generally great value, but Zeiss / Leica / Schneider / etc. are arguably still superior (at much higher prices).

I would call them “good” or “competitive”. There is no such thing as a “best” lens. It’s all about what you are looking for. My “best” lens for portraits is an old manual Pentax lens which is quite flawed but the images just look great.

Ehhhhh...

IDK what they're like nowadays, but Sigma has in the past had a reputation for a larger quality variance than others.

Sigma improved a lot, apprently they developed proprietary testing equipment involving their Foveon sensors.

Old Sigma lenses were often pretty bad, but the new Sigma Art lenses are amazing!

And they moonlight as dumbbells in a gym.