There is a connection between decision and responsibility. Whoever makes the decision takes responsibility. Therefore, if the decision about the technology of metrics is made as part of the macro architecture, then the macro architecture group must take responsibility. For example, they would be responsible if this technology proves unsuitable in the end because it does not cope with the amount of data.
If the responsibility for monitoring microservices is completely transferred to the teams, then the teams must also be allowed to select a technology.
The freedom regarding micro architecture can lead to a huge number of technologies in use. But this is not necessarily the case. If all teams have had good experiences with a particular monitoring technology, then a new microservice will most likely be monitored with the same tool. Using another tool would require a great deal of effort. Other options are only evaluated and used if the tool used so far is insufficient.
Even without a macro architecture rule, there is standardization if uniform decisions bring advantages for the teams. The prerequisite for this is, of course, an exchange between the teams about best practices and about which technologies work and which do not.