There are downsides to KL, but in my opinion its not either of those.

House prices - Not according to https://www.propertyguru.com.my, I looked up Cyberjaya as an example (~15mins on train to KL sentral) and freehold $120,000usd for a 4bedroom/2bathroom place, 1 bedroom condo for much less. That would buy you half a car parking place in Hong Kong (on leasehold no less). Regardless you'd just rent anyway, at least for first few years, $300-$400pm for a nice serviced condo with pool/gym. No point buying unless you eventually get a permanent residence.

English language - I never had a problem with English in KL or Penang or even Alor Setar, except maybe one of the old roadside tea vendors, but that's probably my northern accent. It might not be Singapore or HKG level but it aint significantly off.