There are tons of justifications you can come up with for not using something you don't want to use. The down side is that you aren't going to be getting the upsides you'd get if you used a new technology, possibly to the extent of being no longer competitive with people who do use that technology.
The important thing is balancing chasing the new hotness vs. always using the tried and true.
Last year I ran into a similar sort of situation at work, the funds to buy Ansible Tower required a battle I wasn't willing to fight. The argument was "We've spent so much money on tools that then get abandoned." We spent nearly a year with me being the only one in the company that could run Ansible playbooks because of this, until I finally found RunDeck. Now, we aren't paying for Rundeck, does that make it more likely to be abandoned? Was the risk in our operations if I suddenly became unavailable worth the saved licensing fees? Well, in this case it worked out ok, but it could have gone very badly.
As far as timeseries goes, there are huge advantages here. We used to use collectd/graphite/carbon, but a year or more ago I switched us over to InfluxDB/telegraf/grafana. It was a little rocky a start, the first version of Influx I used had plenty of problems. At the time Prometheus was probably a better choice, but I couldn't come up with a way to make it's pull-centric design fit into our environment. Then InfluxDB settled down and things have been great since.
We have way better metrics, with a way more usable dashboard, and significantly lower load. Literally, disabling collectd ended the complaints about performance on our dev/stg environments.