Pastern angle is very horizontal, but mainly caused by collapsed heels. The hind feet seem very small for the size of horse and not well shaped, which is contributing to the heel collapse.
So you've just posted a picture of someone else's horse that you have no intention of buying? Rather than to help you decide? I was going to ask for a complete body picture to really see what was going on but that really wouldn't be fair so don't.
Many years ago we had a very talented young riding club member. In due course she was bought an unbroken 4 yr old to bring on. We were invited to go and see it and were proudly shown an irish x, bit on the common side, not that that matters but horrendously tied in below knee and hock. Mum then says 'do you think daughter will get to Badminton with her'? I couldn't answer honestly so just said that depends on her. Daughter broke the mare in and 4 weeks later put her in her first xc event. Mare developed really bad bog spavins both hind legs and then broke down in front. Was given 6 weeks off and back to work, you can guess the rest. They moved away thankfully so we no longer had to witness this. Some years later I bumped into mum at a local show. Turned out they still had the mare but used her for breeding now. The daughter was a very talented rider and they gave their horses best of everything but they had no 'horse sense'. Daughter took her BHSAI and sailed through it due to a photographic memory. Pity she didn't actually learn from experience.
Rider ability is very important but a reasonably well conformed horse is essential and those hocks in the picture will not hold up to work beyond very light stuff.