There isn't really an 'industry standard' for 2D animation. Animation productions will often have a mixture of off-the-shelf software and custom tools.

Some well-known apps in the 2D animation space:

- Moho: This has a long history and probably influenced some of the features in Synfig. Moho lets you rig 2D vector models with 'bones' that will save you having to animate frame-by-frame (although you can do that too). https://my.smithmicro.com/moho-pro.html

- Toon Boom: One of the most popular tools in the industry https://www.toonboom.com/

- TVPaint: Also with a long history and requires a dongle to run (remember those?!) https://www.tvpaint.com/

All the above apps are aimed at professionals in the industry, and have a substantial price to match.

CTA4 on the prosumer side, although it comes with more mature 2.5D and upper body / face mocap capabilities.