Debian is on a roughly 2 year release cycle, and typically has a 6 month (-ish) freeze leading up to the release. So software in the stable release will generally be somewhere between 6 months and 2 years out of date. (My math might be a bit off but hopefully you get the idea).

Ultimately, it comes down to how you use your system, and what you need/want from your software. What you consider to be “the things that matter” will really be the deciding factor here. Need the occasional newer version of an application or library? It’s probably fine. Need the latest, greatest desktop environment? You may want to pass.

There are a number of ways to install newer versions. Backports, if it has what you want, is the easiest and safest.

There are other ways as well, but depending on what method you choose and what software it is, you may need to be careful not to break something. (I’d recommend not adding random third-party deb repositories for this reason).

Flatpak seems reasonable, but I haven’t used it much (once or twice I think). I typically use backports, or occasionally do my own local backports from sid.

Snap and AppImage are also possibilities. I don’t use snap, and I think I installed something proprietary by AppImage exactly once.

If it’s not in Debian at all, then I need to handle that a bit differently. But to me that’s a different issue than the ‘old version’ issue that Debian is often derided for.

Anecdotally, I’ve been daily-driving Debian stable (including for gaming) for over 20 years, and it suits my needs well. But of course, YMMV.