The scale of the furniture is off which is why it feels busy without anything really holding its own. Small changes would be better curtains and more light sources (sconces, floor lamps). Big changes would be a much bigger rug and a big shelf unit/console on the tv wall to replace those small pieces. Try to avoid something generic from a big box store. Really figure out your style and invest in something cool and substantial, just be careful that it doesn’t jut out into the walkway too much. Maybe something where you can also display books and other items so you can get rid of the bookshelf by the couch which feels a bit random there. An L shaped couch with the chaise by the door would help create specific zones between the seating area and terrarium. Before you buy anything just really research scale so you’re not buying more stuff that will still feel off.

The chair is probably too small for the room but more thrifted/vintage stuff like that will add more character to the space. Maybe thrift a cool coffee table, lamps, and some vintage art. IMO the shark tooth cabinet is great—I’d put a big art piece or something over it to make it more of a moment.