Don't worry, pretty soon the reliability of standard calls will be roughly the same as most good voice chat apps with the switch for all carriers to implement VoLTE. Maybe still a little more reliable as it won't directly rely on the public internet, but overall still a SIP/IP-based VoIP system as opposed to the dedicated call channels which were the standard previously.
Pretty sure it's due to voice chat apps only has a handful of centralized servers, resulting in more hops, higher latency and worse experience while your telcos has edge servers spread out allowing lower latency voice call between customers in the same geographical areas.