The XP system was removed for balancing reasons plus Zion explained that the demon hunters are on their physical peak and can't progress further in normal ways. Relics, runes, special food and other items are required to increase the stats.
The striptease scene with Iole got removed on purpose for now due to Zion want to build up the relationship for each love interest first. The scene isn't gone for good but gets added again at a more suitable moment.
A new artist wasn't hired for fun but because Kainkout had a hand injury and couldn't progress anymore. The current artist had a hand injury too, ending in a long hiatus for SC and Zion working on Eden Crest to have something to work on in the meantime.
That's why the art changed. Long story short, Kainkout won't come back for SC artworks so you either have to gewt comfy with the new style or find a better game for you.^^