there wasn’t really a Google cloud up until recently. the first google app engine was a bad product and a bad first impression i agree, but it is NOT gcp. you should give it another try today.
your datastore costs were probably ultra high because of exploding indexes. you should have read the documentation to understand what this product is and isn’t (and it is, extremely feature poor).
lastly, every provider can bite you if you don’t know what you’re doing. cloudflare, digitalocean provide very narrow set of compute services so you’re less likely to make mistakes.
There are new monitors (stackdriver) now and alerts to assist, but if you’re constantly over priced then your architecture, most likely, needs to change.