>>38625632>it just get's bigger!...is not an argument. If something get's bigger in a boring way, or if the base form was uncool and the final form failed to make it cooler, then sure, but what OP posted is objectively cool and exciting. Just like Growlithe to Arcanine, Cyndaquil to Typhlosion, Litleo to Pyroar, and many others - fire type and otherwise - it embraces and further emphasizes the raw appeal of its previous forms, a design strategy which once differentiated Pokemon from Digimon and massively contributed to the former's success over the latter. It maintains familiarity and your bond with the base form, while also showing you that your partner has grown with you and matured.
If something's not broken, don't try to fix it, just add some spit and shine and you're good to go. Otherwise you might end up with, uh, this thing...