I hate to say it but I'm pretty disappointed.
TL;DR: Sirfetch'd doesn't look or feel like an evolution to Farfetch'd -- it just looks like a Galarian forme. If it had been a simple Galarian forme I wouldn't be disappointed -- I'd actually have been excited. But the way it is now, you can hardly call it an evolution.
Reasons:
1) Looks. Sure, since the original R/B dex entries, Farfetch'd has been using its leek as a sword. So it does seem like a natural progression to evolve into a proper leek-sword-wielding duck. But it doesn't look like an improvement, it just looks like a white coloured variant that learned how to sharpen its Stick and fashion a shield -- which sounds like the lore for a regional forme, not an evolution. There's no real addition to the design, no added armour or bells and whistles, etc.
2) Typing. The typing is really frustrating. Particularly dropping both of its original typings. There is currently only one analog for this -- Alolan Marowak. But just because there is an analog doesn't make it okay nor does it help it make any more sense. Imo Alolan Marowak should have evolved from a Ground/Ghost or Fire/Ground (or even Fire/Ghost/Fire-Ghost) Alolan Cubone just like all the other Alolan formes. Seeing them repeat that with another classic Pokemon is just sad. It's still literally a bird (as mentioned above, it's basically the exact same bird), and even if it's new utensils make it more difficult to actually fly, it easily could have retained the Flying type to be Fighting/Flying. It's not like there are no Flying types that don't actually fly (ex: Mantine) and it certainly looks like Sirfetch'd could be either a) strong enough to fly while carrying its tools, or b) able to fly without them. Maybe it spent so much time training on the ground that it forgot entirely how to fly / forgot the essence of being a Flying type? It doesn't really make sense. Perhaps it would have been more acceptable had it been a big, burly duck like Buzzwole with a sword or something (and even then probably not), but currently it's just frustrating.