Why is my bath hot water not so hot now that I have new taps?
In general (which is all we can do without specifics of "what new taps") bath and shower controls in the current era include an "anti-scald" feature which deliberately limits how hot the water coming out can be (by some means, which vary, and with more or less effectiveness...)

If replacing older taps, this may well reduce the maximum temperature you can get by a noticeable degree (pun works but not actually intended...)