At what point do you just say "I need a new engine"

My mower seized up recently due to lack of oil. I finally got around to cracking the engine open and found numerous broken parts. The oil sump & block both have cracked metal and are only good for recycling at this point. I also see a broken connecting rod. The camshaft and gears seem viable though. I haven't even taken off the heads and checked the pistons, but my guess is at least one likely has damage, at the very least to the rings.

At what point is replacing parts less favorable than simply buying a new engine? I think based on the damage I see, I just need a new engine at this point given the fact I've never rebuilt an engine. Mind you I'm a complete newb at rebuilding engines, I figured before I just bought a new one I'd take a look how feasible rebuilding one would be with my skills.

Thanks for any advice!

From your description I would say you have reached the point of a new engine. At our shop we have a rule that if a repair costs more than half the cost of a new unit, we recommend replacing and not repairing.

Unless you are looking for a "quality time" project in your workshop with the kids, time to consider a new engine
Like Rivets anything where parts is better than 1/3 to 1/2 the price of a replacement engine I recommend a replacement.
The only exception is top quality engines where there are real bearings & bushes because these engines are always worth repairing.
Run of the mill production engines get replaced.
I no longer refit Briggs Engines as Briggs have abandoned the spares supply in favour of wholesaling Oregon products into supermarkets