I'm playing on Chrome as well and it plays absolutely fluently. Probably your system can't handle it.
Highly unlikely, I have a PC that can handle any game on the highest quality, I'm pretty sure it should be able to handle this game too. XD Maybe in 1995 I would have a PC that couldn't handle this game haha, but it seems to be an issue for alot of people, when the game becomes spammed with monsters (after like 20 min) it's lagging like crazy. On steam it runs fine tho, but still hoping for a switch release. ^^
Haha no, I'm not playing these kinda games on my phone, but I can imagine a phone has slightly less processing power than a PC, so I can imagine it's lagging there indeed ;-) I don't think the Internet connection is the issues, as this is a locally played game as soon as it's downloaded, but there might be some online stuff happening on the background, don't know about that.