I purchased a Helium hotspot last year and was drawn in by what seemed like a real use case for a decentralized system - it made sense to me as far as what value was being provided by miners compared to other PoW cryptocurrencies. I was disappointed by the rewards being somewhat low, but I chalked it up to bad timing.
A few months later, the helium network proposed a change which would take a % of rewards away from hotspot operators and gave it to large holders of the token who have staked it(validators). Sure, this change was 'voted' on - but having more HNT tokens gives you more votes. If large capital holders(at least 50% of the supply seems to be held by the top ~25-30 wallets per https://explorer.helium.com/accounts/richest) can outvote those actually providing utility(hotspot owners), then it doesn't really strike me as a particularly fair and decentralized system.