Just my personal opinion as an Eberron DM in a 5e campaign, and having played and DMed 5e since release, but Artificer is pretty ridiculous. At 10th level, they can attune up to 4 items, at 14th level, 5 items (ignoring requirements, by the way), and at 18th level, 6 items can be attuned. Attunement is a huge balance equalizer in 5e...honestly surprised the designers allowed this. On the other hand, many of their infusions, which are Artificer-created permanent magic items, require Attunement.
Funny thing you can do: infuse an item, have your high-Charisma Deception-proficient friend sell it to a shop keeper or other buyer, then walk away. Shop Keeper can Identify it via normal means (spell or short rest), and see that it appears to be a normal item. Then, infuse an item over your Infused Item limit, expiring the oldest infusion you just sold, leaving the buyer with a mundane item.
Otherwise, great book from what I read so far and nice to see it updated for 5e.